iSNAP2110 Reference Board_Design Guide_w

Accelerating IP Storage Networks
TM
February 24, 2005
SBS 2110 DO 08 1.2.0
iSNAP®
2110
Reference Board
Design Guide
Silverback Systems Confidential

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Silverback Systems Confidential
Copyright © 2002–2005 Silverback Systems. All rights reserved.
This document contains proprietary information of Silverback Systems. No part of the work described herein may be
reproduced. Reverse engineering of the hardware or software is prohibited and is protected by patent law.
This material or any portion of it may not be copied in any form or by any means, stored in a retrieval system, adopted or
transmitted in any form or by any means (electronic, mechanical, photographic, graphic, optic or otherwise), or translated
in any language or computer language without the prior written permission of Silverback Systems.
The information in this document is subject to change without notice. Silverback Systems makes no representation or
warranties with respect to the contents herein and shall not be responsible for any loss or damage caused to the user by the
direct or indirect use of this information. If you find any problems in the documentation, please report them in writing to
Technical Publications at Silverback Systems.
While due care has been taken to deliver accurate documentation, Silverback Systems does not warrant that this document
is error-free.
iSNAP is a registered trademark of Silverback Systems.
Linux is a registered trademark of Linus Torvalds. All other products or company names or trademarks mentioned herein
are used for identification purposes only, and may be trademarks or registered trademarks of their respective owners.
Silverback Systems is located at 655 Campbell Technology Parkway, Campbell, CA 95008. Telephone: 408.558.1200;
Fax: 408.558.1299. For more information about Silverback Systems, visit the Silverback web site at:
www.silverbacksystems.com
SBS 2110 DO 08 1.2.0
2/05

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iSNAP2110 Hardware Reference Manual Silverback Systems Confidential iii
Revision History
Date Version Changes
June 04 SBS 2110 DO 08 1.1.0 External Ethernet cables is Category 5e (see Section 1.4, “System
Requirements”, on page 2).
SYSCLK is an 80 MHz oscillator and MCCLK is a 50 MHz oscillator
with clock buffer (see Section Table 5.1, “Input Clock Source”, on
page 21).
Appendix B:
A minor change to the first paragraph in section B.2.3 DDR
SDRAM Clock Signals
A minor change in B.3.4 SRAM Memory Devices and change in
part number of Cypress control SRAM (see Table B.7,
“Recommended Control SRAM Devices,” on page 42).
February 05 SBS 2110 DO 08 1.2.0 Changed the name of the document from “iSNAP2110 Reference
Board User’s Manual” to “iSNAP2110 Reference Board Design
Guide”
Updated the document to reflect the following:
Half-width memory device support.
Rev 2.0 of the board layout design guidelines (APPENDIX B:
“Reference Board Design Guidelines”)
Removed the Bill of materials (BOM) from this document (the BOM is
included in the design package).

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iv Silverback Systems Confidential iSNAP2110 Hardware Reference Manual

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iSNAP®2110 Reference Board Design Guide Silverback Systems Confidential v
Contents
1 Introduction 1
1.1 Audience 1
1.2 In This Manual 1
1.3 Package Contents 2
1.4 System Requirements 2
1.5 Product Overview 2
1.6 Other Sources of Information 2
1.7 Service and Support 3
2 Reference Board Architecture 5
2.1 Features 5
2.2 Hardware Specifications 6
3 Reference Board Interfaces 7
3.1 RGMII Gigabit Ethernet Interface 7
3.1.1 GE PHY Operating Mode Configuration 8
3.2 DDR SDRAM Memory Interface 8
3.3 Control SRAM Memory Interface 9
3.4 General Purpose Memory Interface 10
3.4.1 Flash Memory Interface 10
3.5 PCI/PCI-X Interface 11
3.5.1 PCI/PCI-X Present Signals 11
3.5.2 PCI Multifunction Support 12
3.5.3 PCI JTAG 12
3.6 JTAG Interface 12
4 Electrical and Mechanical Specifications 13
4.1 Power Consumption 13
4.2 Environmental Specifications 14
4.3 Mechanical Specifications 14
4.3.1 Dimensions 14
4.3.2 Board Stackup 15
4.3.3 Ground Scheme 15

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vi Silverback Systems Confidential iSNAP®2110 Reference Board Design Guide
4.3.4 Mounting Hardware 16
4.4 Connectors 16
4.4.1 RJ45 Connectors 16
4.4.2 JTAG Connectors (Optional) 18
4.4.3 UART Daughter Card Connector (Optional) 18
5 Circuitry and Routing 21
5.1 Clock Circuitry 21
5.2 Reset Circuitry 23
5.2.1 iSNAP2110 Reset 23
5.3 Interrupt Routing 24
6 Setup and Configuration 25
6.1 Configuration and Status Parameters 25
6.1.1 LED Indicators 25
6.1.2 iSNAP2110 Configuration Options 26
6.1.3 General Purpose I/O Pins 26
Appendix A: Reference Board Layout 27
Appendix B: Reference Board Design Guidelines 31
B.1 Characteristics and Definitions 31
B.1.1 PCB Characteristics 31
B.1.2 Definitions 32
B.1.3 System Clocks 32
B.2 DDR SDRAM Interface Layout 34
B.2.1 VREF 34
B.2.2 DDR SDRAM Memory Devices 35
B.2.3 DDR SDRAM Clock Signals 35
B.2.4 Address and Control Signals 38
B.2.5 Data, Data Strobe and Data Mask signals 39
B.3 Control SRAM Interface Layout 40
B.3.1 Address Signals 41
B.3.2 Control Signals 41
B.3.3 Miscellaneous Signals 41
B.3.4 SRAM Memory Devices 41
B.3.5 SRAM Layout Guidelines 42
B.3.6 SRAM Clock 42

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iSNAP®2110 Reference Board Design Guide Silverback Systems Confidential vii
B.3.7 SRAM Data, Data Parity, and Byte Write Enable 43
B.3.8 SRAM Address and Control 43
B.4 GPM Interface Layout 44
B.4.1 Flash Interface 44
B.4.2 UART Daughter Card Connector Interface (Optional) 44
B.4.3 GPM Flash Memory Device 44
B.4.4 GPM Data and Data Parity 45
B.4.5 GPM Address and Control 45
B.5 RGMII Interface Layout 47
B.5.1 RGMII Receive 47
B.5.2 RGMII Transmit 48
B.5.3 PCI(X) 48
Appendix C: Optional Configuration 49
Glossary 51
Index 59

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viii Silverback Systems Confidential iSNAP®2110 Reference Board Design Guide

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iSNAP®2110 Reference Board Design Guide Silverback Systems Confidential ix
Figures
2.1 Reference Board Block Diagram 6
3.1 Gigabit Interface 7
3.2 DDR SDRAM Memory Interface 8
3.3 Control SRAM Interface 9
3.4 GPM Interface 10
3.5 iSNAP Flash Layout for 2 MB Devices 11
3.6 JTAG Chain Configuration Block Diagram 12
4.1 iSNAP2110 Power Regulator BLock Diagram 13
4.2 iSNAP2110 Reference Board Stackup 15
4.3 iSNAP2110 Bracket Block Diagram 16
4.4 RJ45 Bock and Connector Pinout Diagram 17
4.5 UART Daughter Card Connector Pin-Out 19
5.1 iSNAP2110 Input and Output Clock Interface Block Diagram 22
5.2 Reference Board Interrupt Interface Block Diagram 24
A.1 iSNAP2110 Reference Board Layout, Top View 28
A.2 iSNAP2110 Reference Board Layout, Bottom View 29
B.1 PCB Recommended Dimensions 31
B.2 Clock Distribution – MCLK and CPU CLK 33
B.3 Clock Distribution – SYSCLK 33
B.4 VREF Generation 34
B.5 Example of DDR SDRAM Memory Array 35
B.6 DDR SDRAM Routing Guidelines – Clock Signals 36
B.7 DDR SDRAM Clock Topology 37
B.8 DDR SDRAM Address and Controls Topology 38
B.9 DDR SDRAM Data, Data Strobe, and Data Mask Topology 40
B.10 Example ZBT SRAM Memory Array 40

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x Silverback Systems Confidential iSNAP®2110 Reference Board Design Guide
B.11 SRAM Clock Signal Topology 42
B.12 SRAM Data, Data Parity, and Byte Write Enable Topology 43
B.13 SRAM Address and Control Signal Topology 43
B.14 GPM Data and Data Parity Signal Topology 45
B.15 GPM Address and Control Signal Topology – Option 1 46
B.16 GPM Address and Control Signal Topology – Option 2 46
B.17 RGMII Data/Clock ReceiveTopology 47
B.18 RGMII Data/Clock Transmit Topology 48

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iSNAP®2110 Reference Board Design Guide Silverback Systems Confidential xi
Tables
3.1 Default Operating Mode Configuration 8
3.2 DDR SDRAM Data Strobe, Data Mask & Data Bus Mapping 9
4.1 Reference Board Power Consumption 13
4.2 Operating Conditions 14
4.3 Mechanical Specifications 14
4.4 GE Port Connectors 16
4.5 PCI Power and Ground Pins 17
4.6 JTAG Connector Pin-Out 18
4.7 UART Daughter Card Connector Pinout 18
5.1 Input Clock Source 21
5.2 Output Clock Source 22
6.1 BIST LEDs 25
6.2 GE PHY LEDs 26
6.3 iSNAP2110 GPM Strap Options 26
A.1 iSNAP2110 Reference Board Components 27
B.1 VREF Circuitry Relationship 34
B.2 Recommended DDR SDRAM Devices 35
B.3 DDR SDRAM Address and Controls Topology (ending at the center DDR SDRAM) 38
B.4 DDR SDRAM Address and Controls Topology - (starting at the center DDR SDRAM) 38
B.5 DDR SDRAM Address and Controls Topology (for all 20 Address and Control bits) 39
B.6 Data, Data Strobe, and Data Mask 39
B.7 Recommended Control SRAM Devices 42
B.8 Recommended Flash Device 44
C.1 HBA Memory Requirement 49

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xii Silverback Systems Confidential iSNAP®2110 Reference Board Design Guide

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iSNAP®2110 Reference Board Design Guide Silverback Systems Confidential 1
CHAPTER 1 Introduction
1.1 Audience
The iSNAP®2110 Reference Board Design Guide is intended for developers who are designing,
developing, and delivering the Host Bus Adaptor (HBA) boards integrating the iSNAP2110 IP
Storage Network Access Processor into their system for use with their storage applications.
This guide describes the iSNAP2110 Reference Board, which contains the iSNAP2110 device and
ancillary memory devices that allow you to run the iSNAP2110 Reference driver (in a Linux®
environment) and access iSNAP2110 functionality. In addition to describing the board architecture
and the board layout design guidelines, this guide includes a description of various types of
interfaces to the iSNAP2110 Reference Board, generic power, thermal, mechanical, and connector
specifications.
1.2 In This Manual
The iSNAP2110 Reference Board Manual is organized in the following fashion:
Chapter 2, “Reference Board Architecture” provides an overview of iSNAP2110 Reference
Board physical and functional architecture.
Chapter 3, “Reference Board Interfaces” provides a functional description of the major
interfaces of the iSNAP2110 Reference Board.
Chapter 4, “Electrical and Mechanical Specifications” provides a functional description of the
reference board electrical requirements, mechanical, and connector components.
Chapter 5, “Circuitry and Routing” contains clock circuitry, reset circuitry, and interrupts on
the iSNAP2110 Reference Board.
Chapter 6, “Setup and Configuration” covers in detail how to set up and configure the
iSNAP2110 Reference Board.
APPENDIX A: Reference Board Layout illustrates the placement of components on the
APPENDIX B: Reference Board Design Guidelines provides the iSNAP2110 Reference
Board layout guidelines.
APPENDIX C: Optional Configuration provides a description of the iSNAP2110 supported
memory configuration.

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Introduction
2 Silverback Systems Confidential iSNAP®2110 Reference Board Design Guide
1.3 Package Contents
The iSNAP2110 Reference Board is part of the iSNAP21xx System Development Kit (SDK),
which includes, the iSNAP21xx Reference Driver (Linux only), and a complete documentation set.
The iSNAP2110 Reference Board also includes the iSNAP2110 processor. Within the Linux
environment, the iSNAP2110 Reference Board and the iSNAP21xx Reference Driver can be used
to configure your system and test some of the iSNAP2110 processor features (see the iSNAP2110
Getting Started Guide for an overview of suggested test scenarios).
1.4 System Requirements
Following are the minimum system requirements for the iSNAP2110 Reference Board:
Host-based Configuration
PCI-based, Host PC with an available PCI-X or PCI slot
Red Hat® Enterprise Linux® 3.0 operating system (if used with the iSNAP21xx
Reference Driver)
External Ethernet cables – Category 5e, unshielded, twisted pair
In the above configuration, all required power and signals are provided through the PCI interface.
1.5 Product Overview
The iSNAP2110 Reference Board provides a platform for the iSNAP2110 processor.
Dimensions
Height: 3.0 in (7.6 cm)
Length: 6.6 in (16.8 cm)
Operating Temperature: 0°C to 55°C
Host Operating System: Linux (if used with the iSNAP2110 Reference Driver)
Power Consumption: 6.8W typical and 9.97W maximum, with 1MB ZBT SRAM and 64MB
DDR DRAM.
1.6 Other Sources of Information
For an in-depth presentation of the Silverback Systems iSNAP2110 software, hardware design
fundamentals and applications, see the following publications:
Introduction to the iSNAP
iSNAP21xx Device API Reference Manual
iSNAP21xx iSCSI Target Driver API Guide / iSNAP21xx iSCSI and TOE API Guide
iSNAP2110 Hardware Reference Manual
iSNAP Getting Started Guide

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Service and Support
1.7 Service and Support
Silverback Systems provides access to customer support via the Silverback website at the following
address:
http://www.silverbacksystems/support.com
An Account ID and password, supplied by Silverback Systems, is required to access the
information available from this link.

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Introduction

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CHAPTER 2 Reference Board
Architecture
This chapter describes the physical and functional architecture of the iSNAP2110 Reference
Board.
2.1 Features
The iSNAP2110 Reference Board contains the following features:
Dual Gigabit-Ethernet ports compliant with IEEE 802.3Z standard. Both ports offer:
Full Duplex 1000BASE-T with 10/100/1000 speed, automatic MDI/MDIX detection, and
auto-negotiation support.
Reduced Gigabit Media Independent Interface (RGMII) PHY interface, compatible with
RGMII v1.3 specification.
Onboard Memory
Note: See APPENDIX C: “Optional Configuration” for the memory configurations supported.
Up to 128 MB of packet and context buffer memory (DDR SDRAM) using one
iSNAP2110 global memory layer (one chip-select) interface. In this reference board,
DDR SDRAM may be used only in half-width (36-bits) configuration. The default design
uses 64 MB DDR SDRAM for half-width memory operation.
Up to 2 MB of Control Memory (ZBT SRAM) using one iSNAP2110 control memory
layer (one chip-select) interface. In this reference board, SRAM may be used only in half-
width (36-bits) configuration. The default design uses 1 MB ZBT SRAM for half-width
memory operation.
Boot from Flash. Up to 2 MB of Flash memory. The default design also uses 2 MB of
Flash memory.
Host Interface is PCI 2.3 and PCI-X 1.0a specification compliant.The PCI-X and PCI interface
is 64-bit/133 Mhz/100 Mhz/66 Mhz or 64-bit/32-bit/33 MHz/66 MHz interface, respectively.
PCI Multifunction support with 4 interrupts (contact Silverback Systems for support of
multi-function).
D3 Hot and D3 Cold support.
Gigabit-Ethernet port dual LED indicators.
Green LED for Link/Activity indication.
Bi-color LED for speed (1000/100/10) indication.
JTAG – 10-pins JTAG header for JTAG Scan test connector.
On-board reset/clock circuitry.
General purpose LEDs controlled by iSNAP2110 software for code tracing and status
indication.

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Reference Board Architecture
2.2 Hardware Specifications
Figure 2.1 is a functional block diagram of the iSNAP2110 Reference Board. The interfaces and
circuit areas of the board are described in Chapter 3, “Reference Board Interfaces”, and Chapter 5,
“Circuitry and Routing”.
Figure 2.1 Reference Board Block Diagram
The iSNAP2110 Reference Board integrates the iSNAP2110 processor into a working environment
including the required connector interfaces and memory. When it is used in conjunction with the
iSNAP21xx iSCSI Target Driver API Guide / iSNAP21xx iSCSI and TOE API Guide , the
iSNAP2110 Reference Board is functional only in a Red Hat® Enterprise Linux® 3.0 operating
environment. However, drivers can be ported to other operating systems, see “iSNAP21xx Porting
Guide” for details.
2 Pin Header
GE
PHY
GE
PHY
SMBus
CS0n
1MB
ZBT SRAM
iSNAP2110
2MB Flash
64 MB
DDRSDRAM
GPIO
Clocks Input
PCI/PCI-X Connector
PCI/PCI-X
PCI/PCI-X 32/64 bit
33/66/100/133Mhz
3.3V to 2.5V
3.3V to 1.5V
Source from
50Mhz Osc
10-pins
JTAG
Header
Power Soucce
Clock Distribution
MCLK
CPU_CLK
MDIO
Management I/F
Shielded RJ45 Connector with
integrated Gigabit Ethernet
Magnetic Transformer and LEDs
RJ-45
RJ-45GE
Port 1
GE
Port 0
RGMII
RGMII
JTAG
Source from
80Mhz Osc
SYS_CLK
25Mhz
REFCLK
25Mhz
REFCLK
half-width
operation
half-width
operation

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CHAPTER 3 Reference Board Interfaces
This chapter provides descriptions of the following interfaces on the iSNAP2110 Reference Board:
RGMII Gigabit Ethernet Interface
DDR SDRAM Memory Interface
Control SRAM Memory Interface
General Purpose Memory Interface (Flash Memory)
PCI/PCI-X Interface
JTAG Interface
3.1 RGMII Gigabit Ethernet Interface
The iSNAP2110 Reference Board provides two Gigabit-Ethernet ports (see Figure 3.1) to carry IP
traffic from the network to the iSNAP2110 processor using CAT-5e cable.
Figure 3.1 Gigabit Interface
Both GE ports support full duplex 10/100/1000 speed with automatic MDI/MDI-X crossover
detection and auto-negotiation. A straight cable or a crossover cable can be used to connect the
Reference Board to a switch or another Reference Board. The GE PHY interfaces to the
iSNAP2110 MAC through RGMII interface. The GE interface connects to the shielded RJ-45
connector through an integrated Gigabit Ethernet magnetic transformer and LED. A 25 Mhz
external crystal clock inputs to the GE PHY is used for REF_CLK input.
The MDIO Management Interface provided by iSNAP2110 is shared by both GE PHY ports. To
access a specific PHY port, the software must specify the GE PHY address as follows:
GE PHY Port 0 Interface: PHY address 0x00h.
GE PHY Port 1 Interface: PHY address 0x01h.
GE Port 1
GE Port 0
MDIO Mgmt I/F
RJ-45
Connector
PHY
PHY
iSNAP
Processor
RJ-45
Connector
RGMII
RGMII
Shielded RJ45 Connector with
integrated Gigabit Ethernet
Magnetic transformer and LEDs
25MHz
REFCLK
25MHz
REFCLK

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Reference Board Interfaces
3.1.1 GE PHY Operating Mode Configuration
The mode10/100/1000BaseT inputs force or presents the advertised link capabilities (speed and
duplex) of the GE PHY. The FRC_DPLX (Force Duplex Mode) pin when set high indicates
“duplex mode”. The ANEG_DIS (Auto-Negotiation Disable) pin when set low indicates
“auto-negotiation enable”. When FRC_DPLX pin, ANEG_DIS pin and all of the MODE pins are
left unconnected, the default termination setting is 10/100/1000BaseT full duplex, auto-negotiation
enabled, MDI crossover enabled, energy detect enabled, and 125MHz clock out disabled.
Configuration options may be overwritten by register writes to the PHY with the exception of the
physical address (see Chapter 8, “Registers”, in the iSNAP2110 Hardware Reference Manual).
Table 3.1 shows the default hardware operating mode configuration.
3.2 DDR SDRAM Memory Interface
DDR SDRAM acts as a data buffer for the iSNAP2110 and stores communication data between the
iSNAP2110 and the Host. A single layer half-width memory of DDR SDRAM memory interface to
the iSNAP2110 processor is shown in Figure 3.2.
Figure 3.2 DDR SDRAM Memory Interface
The DDR SDRAM half-width data path allows stuffing option for using only the lower half of the
memory device (by appropriately setting the DDR SDRAM controller). The stuffing option
supports devices with a minimum of 32 MB (2 128Mb x16 devices) and a maximum of 128 MB (2
512Mb x16 devices) memory size. The half-width memory data bus width is 32-bits for data plus
4-bits for ECC that ensure data integrity. (The remaining 4-bits of DDR SDRAM in the ECC data
device data mask are not used).
Table 3.1 Default Operating Mode Configuration
ANEG_DIS FRC_DPLX MODE10 MODE100 MODE1000 Effect
0
(Internal Pull
down) Low
1
(Internal Pull
up) High
1
(Internal Pull
up) High
1
(Internal Pull
up) High
1
(Internal Pull
up) High
Advertise 10/100/1000Base-T
full duplex mode, Auto-
Negotiation Enable.
Data ECC
DDR SDRAM
x16
iSNAP2110
DDR SDRAM
x16
DDR SDRAM
x16
32
432-bit data + 4-bit data parity

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Control SRAM Memory Interface
Table 3.2 shows the data strobe, data mask, and data bus mapping table.
3.3 Control SRAM Memory Interface
The Control SRAM stores iSNAP2110 internal data structures. Figure 3.3 shows the half-width
Control SRAM interface to the iSNAP2110 processor.
Figure 3.3 Control SRAM Interface
The Control SRAM half-width data path allows stuffing option for using only the lower half of the
memory device (by appropriately setting the SRAM control register). The stuffing option supports
devices with a minimum of 1 MB (x 36, 9Mb) and a maximum of 2 MB (x 36, 18Mb) memory size.
The half memory data bus width is 36-bits, 32-bits for data and 4-bits for parity or ECC to ensure
integrity.
Table 3.2 DDR SDRAM Data Strobe, Data Mask & Data Bus Mapping
Data Strobe
Signal
Data Mask
Signal
Data Bus Byte
Masked
Connection
DDR_DS[8] DDR_DM[8]
DDR_CB[7:4] Not Connected
DDR_CB[3:0] To ECC DDR SDRAM I/F
DDR_DS[7] DDR_DM[7] DDR_D[63:56] Not Connected
DDR_DS[3] DDR_DM[3] DDR_D[31:24] To DDR SDRAM 2
iSNAP2110
ZBT SRAM
x36
32-bits data +
4-bits data parity

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3.4 General Purpose Memory Interface
The General Purpose Memory (GPM) consists of Flash memory. Figure 3.4 illustrates the GPM
interface.
Figure 3.4 GPM Interface
The GPM bus interface is 16-bits wide and runs 2.5V LVCMOS (3.3V tolerant) I/O. The
iSNAP2110 Reference Board uses GPM_CS0n chip select for Flash interface and GPM_CSn[3]
for the UART daughter card interface.
3.4.1 Flash Memory Interface
The Flash Memory interface is 16-bits wide, runs 2.5V I/O, and supports up to 2MB. The system
uses chip select GPM_CS0n to access Flash memory (see Figure 3.4). The Flash memory
contains the default configuration parameters and run time code for the iSNAP2110 processor. It
contains the Basic Boot Code required to bootup the iSNAP system. (For information on upgrading
the Boot Code, see the Release Notes.)
Note: The iSNAP2110 supports CFI (Common Flash Memory Interface) Flash devices1.
1. Current version the Firmware (Boot Loader) requires CFI compliant Flash device.
iSNAP2110
GPMBusx16
Flash
x16
UART
Ready
Connector
G PM _CS3_n
Stuff O ption
G PM Bus x8
GPM _CS0_n

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PCI/PCI-X Interface
Flash Layout Granularity
The iSNAP2110 requires the following granularity of the Flash layouts to support 1 MB or 2MB
Flash memory devices:
Figure 3.5 iSNAP Flash Layout for 2 MB Devices
3.5 PCI/PCI-X Interface
The iSNAP2110 Reference Board has a PCI/X interface for communication with the Host and for
supplying power and reset to the iSNAP2110 processor. The system is compliant with the PCI 2.3
and PCI-X 1.0a specifications. Depending upon the Host system slot used, the system is capable of
the following frequencies:
PCI 32/64 bit, 33MHz/66MHz or PCI-X 64 bit, 66MHz/100MHz/l33MHz
I/O voltage, 3.3V DC
Form factor – short, variable height PCI card
The iSNAP2110 Reference Board is considered an Expansion or Add In board in PCI terminology
and is both master (Initiator) and slave (Target) capable. The iSNAP2110 Reference Board is a
single PCI load, indicating that no more than one PCI device (iSNAP2110 processor) is present on
board.
3.5.1 PCI/PCI-X Present Signals
The PRSNT1# and PRSNT2# pins must be terminated appropriately on an expansion board. These
pins indicate to the Host system that an expansion board is present in the slot and provides the total
power requirements information of the iSNAP2110 Reference Board. PRSNT1# is grounded, and
PRSNT2# is open indicating that the total power required is more than 14W but less than 25W.
Basic Boot
(16KB) [0to16KB]
ExtendedBoot
(32KB) [16 to 48KB ]
sysCfg
(8KB) [48 to 56KB]
Mandatory
Crash Dump
(256KB) [64 to 320KB ]
User Data
(192KB) [320 to 512KB]
Application
(512KB)
Optional
roCfg
(8KB) [56 to 64KB]
[For 1 MB Flash 512 to 1024KB]
Note: The values in Italics/Blue show the sectors offset
and indicates the successive sectors for the
Flash layout.
[For 2 MB Flash 512 to 2048KB]

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3.5.2 PCI Multifunction Support
PCI Multifunction supports four interrupts. The PCI interface INTA#, INTB#, INTC#, and
INTD# pins are used to route iSNAP2110 interrupts to the Host.
3.5.3 PCI JTAG
The iSNAP2110 Reference Board does not support PCI JTAG, but PCI_TDO signal connects to
PCI_TDI to ensure that the PCI JTAG scan chain is not broken.
3.6 JTAG Interface
The iSNAP2110 Reference Board has a connector for interfacing the iSNAP2110 to a JTAG Test
Access Port (TAP) emulator in JTAG mode. The iSNAP2110 input pin AK29, JTAG_MODE will
normally be tied to ground to indicate JTAG operation.
The Reference Board provides a boundary-scan chain. It is a fairly simple chain comprised of
cascading the TDI and TDO iSNAP2110 signals with the GE PHY devices. The JTG_TCK,
JTG_TMS and JTG_TRSTn signals are connected to all the components in parallel.
Figure 3.6 JTAG Chain Configuration Block Diagram
JTAG_MODE
iSNAP2110
R
V33
Flash
RESET_N
JTG_TDI
JTG_TMS
JTG_TCK
JTG_TRST_N
JTG_TDO
PCX_RST_N
R
R
V33
R
V33
JTG_TDI
JTG_TDO
iSNAP_RST_OUTn
PCX_RSTn
JTG_TCKJTG_TMS JTG_TRSTn
GE PHY1
RSTn
JTG_TRSTnJTG_TCKJTG_TMS
JTG_TDO
JTG_TDIJTG_TDO
JTG_TDI
GE PHY0
RSTn
JTG_TRSTnJTG_TCKJTG_TMS
4.7KΩR=

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CHAPTER 4 Electrical and Mechanical
Specifications
This chapter includes the power, thermal, mechanical, and connector specifications for the
4.1 Power Consumption
The Reference Board regulates power down from 3.3V to 2.5V, and 1.5V using onboard voltage
regulators. The 2.5V power plane will support I/O buffers and core logic of third party devices.
The 1.5V power plane will support the iSNAP2110 core logic and GE PHY. Table 4.1 shows the
iSNAP2110 Reference Board power consumption, which meets the maximum power consumption
limit.
Figure 4.1 iSNAP2110 Power Regulator BLock Diagram
Table 4.1 Reference Board Power Consumption
Description Maximum Power
Consumption [W]a
a. These are worst-case calculated values.
3.3V plane 0.97
2.5V plane 4.30
1.5V plane 4.60
Total system 9.97
V33
V33
PCI/PCI-X Connector
3.3V to 1.5V
regulator
6A (max)
3.3V to 2.5V
regulator
3A (max)
iSNAP2110ReferenceBoard

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Electrical and Mechanical Specifications
4.2 Environmental Specifications
Table 4.2 lists the iSNAP2110 Reference Board operating conditions.
4.3 Mechanical Specifications
4.3.1 Dimensions
The reference board complies with the PCI/PCI-X form factor. Its physical characteristics are
detailed in Table 4.3.
Table 4.2 Operating Conditions
Temperature Operating: 0°C to 55°C
Storage: - 40°C to +125°C
Voltage 3.3V (±10%)
Humidity Operating: Relative (non-condensing:10% to 90%)
Storage: 5% to 95%
Table 4.3 Mechanical Specifications
Reference Board Specifications
Board Dimensions: Length: 6.6 in. ± 0.005 inches
Height: 3.0 in ± 0.005 inches
Thickness: 0.062 in. ± 0.008 inches
Maximum Component Heights: Component side: 570 mils
Solder side: 105 mils

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Mechanical Specifications
4.3.2 Board Stackup
Figure 4.2 illustrates the iSNAP2110 Reference Board stackup.
Figure 4.2 iSNAP2110 Reference Board Stackup
4.3.3 Ground Scheme
The grounding scheme includes one layer divided into two separate ground planes: signal ground
and chassis ground. The chassis ground islands run the height of the board from top to bottom and
are separated from the signal ground planes underneath the Gigabit Ethernet components (RJ45).
prepreg 0.0037
0.0140CORE
prepreg 0.0035
0.0100CORE
prepreg 0.0035
0.0140CORE
prepreg
SIG/PLANEL1
SIGNALL2
SIGNALL4
SIGNALL5
SIGNALL7
0.0037
SIG/PLANEL8
FR4-6
(inches)
Layer Copper
(Oz)
L3 PLANE
L6 PLANE
55
Z
0(Single Ended )
W(Single Ended )
Differential Z0 = xx Ω
Ω
55Ω
55Ω
55Ω
55Ω
55Ω
(inches)
Layer Type
W is the finished line width
0.00425
0.00425
0.00400
0.00425
0.00425
0.00400
W
(Differential )
(inches)
0.0075
0.0075
0.0080
0.0075
0.0075
0.0080
D(Differential )
(inches)
D is the finished line space
Note:
0.0037
0.0140
0.0035
0.0100
0.0035
0.0140
0.0037
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.0045
0.0041
0.0041
0.0045
0.0041
0.0041

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4.3.4 Mounting Hardware
A bracket is provided on the rear panel edge of the board for mounting the board in a standard PCI
or PCI-X slot. This allows the RJ45 connectors and LEDs to be visible and accessible when the
chassis is closed.
Figure 4.3 iSNAP2110 Bracket Block Diagram
4.4 Connectors
The iSNAP2110 Reference Board requires the following connectors:
Two RJ45 connectors required for the copper Gigabit Ethernet ports.
One PCI/X Connector.
One JTAG connector (optional).
Note: Refer to Appendix A (in development) for the placement of the connectors and their
dimensions.
4.4.1 RJ45 Connectors
The RJ45 connectors provide copper Ethernet connectivity to the Host via Port 0 and Port 1.
Table 4.4 describes pin assignments for the GE interface connectors on the iSNAP2110 Reference
Board.
Table 4.4 GE Port Connectors
Pin 1 2 3 4 5 6 7 8
Signal DA_P DA_M DB_P DC_P DC_M DB_M DD_P DD_M
PORT1
Silverback
Systems
PORT0

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Connectors
Figure 4.4 RJ45 Bock and Connector Pinout Diagram
The PCI connector used on the iSNAP2110 Reference Board also provides 3.3V and 5V power to
the board. Figure 4.5 lists the power and ground pins.:
Table 4.5 PCI Power and Ground Pins
Pin# Description
B19 B25 B31 B36 B41 B43 B54 B59 B70 B79 B88
A10 A16 A21 A27 A33 A39 A45 A53 A59 A66 A75 A84
+3.3V
B3 B15 B17 B22 B28 B34 B46 B50 B51 B57 B64 B67 B73 B76 B82 B85 B91 B94
A18 A24 A30 A35 A37 A42 A48 A50 A51 A56 A63 A69 A72 A78 A81 A87
A90 A93
GND
B5 B6 B61 B62 A5 A8 A61 A62 +5V
1 2 3 4 5 6
7 8 9 10 11 12
13 14 15 16
iSNAP2110ReferenceBoard

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4.4.2 JTAG Connectors (Optional)
An on-board 10 pin JTAG header is used to access the iSNAP2110 JTAG interface. The JTAG
header is a dual line, 2 Rows by 5 Pin connector. The JTAG pin assignment is shown Table 4.6.
4.4.3 UART Daughter Card Connector (Optional)
The UART daughter card connector is for development purposes only. The card has a provision for
a 40 Pin, part number: AMP-TYCO 17902-1 connector interface. Figure 4.5 shows the Uart pin out
diagram.
Table 4.6 JTAG Connector Pin-Out
Pin # Description Pin# Description
1 TCK – Test Clock In 2 GND – Ground
3 TDO – Test Data Out 4 VCC (3.3V)
5 TMS – Test Mode Select 6 TRST_N
7 N/C - Not connected 8 N/C – Not connected
9 TDI – Test Data In 10 GND – Ground
Table 4.7 UART Daughter Card Connector Pinout
Pin Signal Name Pin Signal Name
1 GND 2 V3.3
3 GND 4 V3.3
5 GND 6 V3.3
7 GND 8 V3.3
9 INT 10 ISNAP_RST_OUTn
11 NC 12 GPM_WE_N
13 GPIO[1]/GPM_CSn[3] 14 NC
15 GPM_A[2] 16 NC
17 GPM_A[1] 18 NC
19 GPM_A[0] 20 GPM_D[7]
21 NC 22 GPM_D[6]
23 NC 24 GPM_D[1]
25 NC 26 GPM_D[2]
27 GPM_OEn 28 GPM_D[5]
29 GPM_D[0] 30 GPM_D[4]
31 NC 32 GPM_D[]3]
33 V3.3 34 GND

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Connectors
Figure 4.5 UART Daughter Card Connector Pin-Out
35 V3.3 36 GND
37 V3.3 38 GND
39 V3.3 40 GND
Table 4.7 UART Daughter Card Connector Pinout (Continued)
Pin Signal Name Pin Signal Name
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40

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CHAPTER 5 Circuitry and Routing
This chapter provides descriptions of the following circuit and interrupts on the iSNAP2110
Reference Board:
Clock Circuitry
Reset Circuitry
Interrupt Routing
5.1 Clock Circuitry
The iSNAP2110 receives clock inputs from a number of sources and generates clock outputs. All
clocks are LVCMOS logic level. The input clock sources are described in Table 5.1.
Figure 5.1 shows the iSNAP2110 and the system level clock (both input and output clocks)
interface block diagram.
Table 5.1 Input Clock Source
iSNAP2110 Input Clock Frequency Source Type External, Oscillator
PCX_CLK 33/66/100/ 133MHz PCI/PCI-X host computer
CPUCLK 50MHz External 50 MHz Osc with clock buffer
SYSCLK 80MHz External 80 MHz Osc
MCLK 50MHz External 50 MHz Osc with clock buffer
GPP_CLK Not used Not used
GMACCLK Not used Not used
GE0_RXCLK 2.5/25/125Mhz From GE0
GE1_RXCLK 2.5/25/125Mhz From GE1
TCK adjustable External JTAG

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Circuitry and Routing
Figure 5.1 iSNAP2110 Input and Output Clock Interface Block Diagram
The output clock sources are described in Table 5.2.
Table 5.2 Output Clock Source
iSNAP2110 Output Clock Frequency Source Type
Internal, PLL
Logic Levels
SRM_CLK 125MHz PLL (=2.5*MCLK) 2.5V LVCMOS
SRM_DUP_CLK (not used) 125MHz PLL (=2.5*MCLK) 2.5V LVCMOS
GPM_CLK (Not used) 125MHz SRM_CLK Internal 2.5V LVCMOS
iSNAP2110
OSC
50Mhz
MCLK
CPU_CLK
SYS_CLK
QMS
SRAM
QMS
SRAMSRM_CLK
GE 0
DDR
SDRAM
GE0_GTXCLK
GE 1
GE1_GTXCLK
DDR
SDRAM
DDR
SDRAM
DDR_FBK_CLK_P/N
DDR_CLK[0]_P/N
DDR_CLK[2]_P/N
x16 ECC
2.5/25/125Mhz
150Mhz
150Mhz
25Mhz
125Mhz
50Mhz
80Mhz
GE1_RXCLK
GE0_RXCLK
x16
x16
PCX_CLK
2.5/25/125Mhz
GMACLK
2.5/25/125Mhz
2.5/25/125Mhz
0 ohm
NO_LOAD
CLK125
CLK125
From PCX connector
OSC
80Mhz
CDCV304
REF_CLK
25Mhz
REF_CLK
PHY1_CLK
PHY2_CLK
NC
NC
NC = Not Connected
DDR_CLK[1]_P/N
NC

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Reset Circuitry
5.2 Reset Circuitry
The PCI-X Pin (PCX_RSTn) resets the iSNAP2110. The iSNAP2110 signal,
iSNAP_RST_OUTn, resets the Flash, GE PHY, and UART devices. The JTG_TRSTn input pin
of the iSNAP2110 and GE TRSTn pin are typically tied down but can be connected to the
JTG_TRSTn input, using the appropriate stuff option. See Figure 3.6, “JTAG Chain Configuration
Block Diagram,” on page 12 for the reset circuitry.
5.2.1 iSNAP2110 Reset
The input pin, the PCI-X reset signal (PCX_RSTn) will reset the iSNAP2110. The output pin
(RST_OUTn), of the iSNAP2110 contains the qualified internal chip reset. This active low
qualified Reset Output from the iSNAP2110 is the input to the Boot Flash and GE PHYs (see the
iSNAP2110 Hardware Reference Manual for details).
FLH_CLK (Not used) f/2 or f/4, f=GPMClk Internal 2.5V LVCMOS
DDR_CLK[2]/_N 150 MHz PLL (=3*MCLK) SSTL-2 Differential
DDR_CLK[1]/_Na
150 MHz PLL (=3*MCLK) SSTL-2 Differential
DDR_CLK[0]/_N 150 MHz PLL (=3*MCLK) SSTL-2 Differential
GE1_GTX CLK 2.5/25/125 MHz SRM_CLK(/50,/5,/1)
Internal
2.5V LVCMOS
GE0_GTXCLK 2.5/25/125 MHz SRM_CLK(/50,/5,/1)
Internal
2.5V LVCMOS
PHY1CLK Not used Internal, SYS_CLK
input /2
2.5V LVCMOS
PHY2CLK Not used Internal, SYS_CLK
input /2
2.5V LVCMOS
a. Not connected.
Table 5.2 Output Clock Source (Continued)
iSNAP2110 Output Clock Frequency Source Type
Internal, PLL
Logic Levels

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Circuitry and Routing
5.3 Interrupt Routing
The iSNAP2110 interrupt input pin is driven by one of the GE PHY interrupts—both selectable by
0 ohm resistors or by the UART interface. The iSNAP2110 sends an interrupt to the Host via any of
the PCI/X signal INTx# in a Host-based configuration (see the iSNAP2110 Hardware Reference
Manual for details).
Figure 5.2 Reference Board Interrupt Interface Block Diagram
iS N A P 2110
G E PHY0
INT#
PCI/PCI-XConnector
G E PHY1
INT#
INTA#
INTn
INTD#
INTC#
INTB#
R
2.5V
UARTdaughter
cardConnector
N ote: U A R T daughter card inverts
the interrupt to drive low

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CHAPTER 6 Setup and Configuration
This chapter describes the installation and configuration of the iSNAP2110 Reference Board.
6.1 Configuration and Status Parameters
The operational status of the iSNAP2110 Reference Board is indicated by a set of onboard LEDs
indicating BIST status and GE port status.
6.1.1 LED Indicators
6.1.1.1 BIST LEDs
BIST LEDs indicate development and debugging status, which are shown in Table 6.1.
Table 6.1 BIST LEDs
BIST bits LED Description
ISNAP_BIST<0> DS1 BIST self test indication for successful boot up
from the Flash image
ON: Pass
OFF: Fail
ISNAP_BIST<1> DS2 BIST self test indication for DDR SDRAM Test
ON: Pass
OFF: Fail
ISNAP_BIST<2> DS3 BIST self test indication for ZBT SRAM Test
ON: Pass
OFF: Fail

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Setup and Configuration
6.1.1.2 Gigabit-Ethernet LEDs
Gigabit Ethernet activity, link and speed status are provided by the RJ45 modules. The GE PHY
LEDs are shown in Table 6.2.
6.1.2 iSNAP2110 Configuration Options
There are twenty pins of the iSNAP2110 GPM address bus, which are sampled on power up to
direct the iSNAP2110 to configure itself in various states. GPM_SA[19:14, 12:0] use their default
value, and GPM_SA[13] must be pulled up through a 470 ohm resistor to 2.5V. The strap option is
shown in Table 6.3.
6.1.3 General Purpose I/O Pins
There are eighteen pins on the iSNAP2110, which can be used as General Purpose inputs or
outputs (GPIOs). Some of the pins have predefined usage in the iSNAP firmware. Each of the
GPIO pins can be used either in its normal function for one of the modules within the iSNAP2110,
or as a GPIO. See Section “3.6 GPIO Interface” of the“iSNAP2110 Hardware Reference Manual”
for a list of functional Pins used as general purpose I/O Pins.
Table 6.2 GE PHY LEDs
GE LED LED Color Description
Link Status
(10/100/1000 Speed)
Bi-Color LED
Green/Orange
GREEN: 1000 speed
ORANGE: 100 speed
OFF: 10 speed.
Link Activity Green ON: Link is established
OFF: Link is NOT established
Blinking: Activity
Table 6.3 iSNAP2110 GPM Strap Options
Strap
Source
Strap Name Strap Description Resistor
Default
Value
GPMSA[13] bypass_sys_PLL_out Bypass PN PLL PLLoutB and use
system oscillator for system clock
R34 Pull Up
(High)

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APPENDIX A: Reference Board Layout
Table A.1 lists the key components on the Reference Board Layout. (A complete the Bill of
Materials is included with the design package.) These components are identified in both the top
view and bottom view of the Reference Board. Figure A.1 and Figure A.2 refers to Reference
Board Revision 2.0.
Note: The columns labeled “Item No.” and “Ref. No.” refers to the columns labeled the same in
the Bill of Materirals (BOM) included witht the design package.
Table A.1 iSNAP2110 Reference Board Components
Item No. Ref. No. Description
Top View
18 U1 Storage Network Processor, ISNAP2110
16 U7 Flash 1Mb x 16, 70ns, 48TSOP
15 U2, U11, U15 DDR SDRAM 256 Mb, 16 MB x16, SSTL-2
19 U8 ZBT SRAM, 9Mb, 256KbX36, 167MHZ, 2.5V
20 U9, U14 Gigabit-Ethernet PHYs (10/100/1000)
22 U4, U13 RJ-45 Conenctors
11 DS1-DS3 BIST status LEDs
12 U3 Voltage Regulator, 3.3V to 2.5V
13 U12 Switch Regulator 3.3V to 2.5V
14 U10 1:4, 8-Pin TSSOP Clock Buffer
41 X1, X3 Crystal 25 MHz
42 X4 Oscillator 50 MHz
43 X2 Oscillator 80 MHz
21 J2 JTAG (10 Pins)
Bottom View
Optinal
(Not Stuffed)
J3 UART I/F board-to-board connector

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Figure A.1 iSNAP2110 Reference Board Layout, Top View
U2
Item No: 15
U11
Item No: 15
U15
Item No: 15
J2
Item No: 21
U8
Item No: 18
U7
Item No: 16
U4
Item No: 22
U13
Item No: 22
U14
Item No: 20
U9
Item No: 20
X3
Item No: 41
X1
Item No: 41
X4
Item No: 42
U10
Item No: 14
X2
Item No: 43
U1
Item No: 18
U3
Item No: 15
U12
Item No: 12

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Figure A.2 iSNAP2110 Reference Board Layout, Bottom View
J3 - Not stuffed
UART Connector

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APPENDIX B: Reference Board Design
Guidelines
This chapter describes the Silverback Systems Reference Board design guidelines and
recommendations. The chapter includes: guidelines for the board layout of the external DDR
SDRAM, ZBT SRAM, and GPM memory interfaces as well as the RGMII and PCI/PCI-X
interfaces. Topics addressed include choice of memory device, placement of parts, maximum trace
length, and routing requirements as well as power, grounding and impedance characteristics. For
detailed information on the iSNAP2110, please refer to the iSNAP2110 Hardware Reference
Manual.
Note: The layout guidelines are based on the iSNAP2110 ver2.0 Reference Board simulation.
B.1 Characteristics and Definitions
B.1.1 PCB Characteristics
That following is a general guideline for the PCB characteristics of all the interfaces. The actual
dielectric coefficient, thickness and copper weight will be determined by the PCB fabrication
facility along with the designer, taking in count:
Layer count.
Desired typical impedence (Z0).
Cost.
Total board thickness and size.
Figure B.1 PCB Recommended Dimensions
To achieve the required timing and Signal Integrity (SI), the PCB should follow these
recommendations:
Controlled impedance: single ended, Z0 = 50Ω, and differential Z0 = 100Ω.
The trace width W (see Figure 4.2 on page 15) is determined by the relative Dielectric
Coefficient Er, and the available thickness of dielectric H, and is calculated to achieve 50Ω.
Trace separation is S ≥ 2 x W (center-to-center).
W
S
H
S = Trace Separation
W = Trace Width
H = Dielectric thickness

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Characteristics and Definitions
General layout considerations:
Traces should be routed with a minimum numbers of vias and minimum layer switching.
All signals are routed in layers that are adjacent to the GND planes.
Note: Extra care should be taken when placing and routing the board to meet timing budget and
avoid SI problems.
B.1.2 Definitions
This section describes the terminology used in this appendix.
Extended Net – An extended net intersects one or more passive device (resistor, inductor or
capacitor). Each net segment is represented by an individual transmission line in the topology.
Pin-Pair – A pair of logically connected pins, e.g., a driver-receiver connection. A group1
of
pin-pairs need not be directly connected to each other but must exist on the same net or
extended net.
Target pin-pair – One of the pin-pairs explicitly defined as the target within a group of
pin-pairs. All the other pin-pairs in the group are matched against this target pin-pair within
the given delta2
and tolerance3
. Within a group of pin-pairs:
If all the pin-pairs have a delta value, the pin-pair with the smallest delta value is selected
as the target pin-pair.
If more than one pin-pair has the same (smallest) delta value, the pin-pair with the longest
length is selected as the target.
Note: The target pin-pair is referenced by all the other pin-pairs within a group of pin-pairs.
B.1.3 System Clocks
The clock inputs to the iSNAP2110 (MCLK, CPUCLK, and SYSCLK) are single ended
(Figure B.2 and Figure B.3). The 50MHz oscillator drives a 1:2 clock buffer with one output each
connected to MCLK and CPUCLK. The trace lengths should be as short as possible. An 80 MHz
oscillator drives the SYSCLK input. The following are the design recommendations:
Route the clocks next to a GND layer with a minimum of vias.
To avoid crosstalk, separate clock signals from other signals. Clock signals should be
separated from other signals by a distance of S, which is at least three times the trace width
(i.e., X ≥ 3W – see Figure B.1).
Keep the clocks away from the edge of the board and any connectors.
1. Group of pin-pairs – a user-specified collection of pin-pairs constrained by a match length.
2. Delta – the difference between each pin-pair and the target pin-pair. If the delta is zero, all the pin-pair are
required to match. For example, here all deltas are 0 mils
3. Tolerance – the skew allowed when matching a group of pin-pairs. For example, ±50 mils, indicate that
the range between the shortest and longest pin-pairs is 100 mils. The target pin-pair has 0 mils tolerance.

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Figure B.2 Clock Distribution – MCLK and CPU CLK
Figure B.3 Clock Distribution – SYSCLK
Segment L11 L12
Lengtha
a. All trace lengths are in inches
0.25” As short as possible
Matching From pin to pin (L11+L12) one pin-pair
should be = the target pin-pair ±50 mils
Segment L21 L22
Lengtha
0.25” As short as possible
Matching N/A
Clock Buffer CDCV
50 MHz
MCLK
CPU CLK
33Ω
L11 L12
33Ω
L11 L12
OSC
iSNAP2110
80 MHz
SYS CLK
33Ω
L21 L22OSC
iSNAP2110

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DDR SDRAM Interface Layout
B.2 DDR SDRAM Interface Layout
This section outlines the necessary layout guidelines for a board with iSNAP2110 and a DDR
SDRAM interface (see Table B.2). The DDR SDRAM interface is designed to run at a frequency
of 150MHz. The DDR SDRAM samples the data at both rising and falling edges of the strobe. The
address and controls are sampled at the rising edge of the clock.
B.2.1 VREF
The following JEDEC SSTL-2 standard for VREF circuitry relationship ensures successful
operation of the DDR SDRAM (Table B.1):
1. VREF will sink very low current (leakage current).
2. VREF should be implemented with a local voltage divider per each DDR SDRAM component
and iSNAP2110 VREF. This is to enable tracking of the local VDD of the specific component.
The two thevenin resistors should be placed very close to their corresponding component
(Figure B.4).
Figure B.4 VREF Generation
Table B.1 VREF Circuitry Relationshipa
a. All voltages are referenced to Vss, which is defined as the device GND.
Symbol Parameter Min Type Max Units
VDD Device Supply Voltage VDDQ N/A V
VDDQ Output Supply Voltage 2.3 2.5 2.7 V
VREF Input Reference Voltage 1.15 1.25 1.35 V
4.7K 1%
4.7K 1%
VDDQ
VREF
VTT
VTTIslandclosetoMemories
RpackRpackRpack
Cap
Cap
Cap
Cap
Cap
1.25V
VRM0.1µF
0.1µF

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B.2.2 DDR SDRAM Memory Devices
The choice of memory depth and width will affect the part count for the DDR SDRAM memory
subsystem design. This section covers the x16 width with three devices per memory array4
(Figure B.5). The iSNAP2110 is capable of supporting a maximum of 4 memory arrays using the
four chip select signals (CS0_N - CS3_N).
Figure B.5 Example of DDR SDRAM Memory Array
Note: The iSNAP2110 does not prevent the designer from choosing other topologies, as the
principles used in the three devices per memory array design may be scaled down or
extended.
If DDR SDRAM (256 Mb – 16Mb x 16) devices are used, the amount of memory will be 64 MB
per memory array. In a dual memory array subsystem, these devices will output a total capacity of
128 MB. In a quad memory array subsystem, these devices will output a total capacity of 256 MB.
The DDR SDRAM devices used on this reference design are in a 66 pin TSOP package available
from companies such as Samsung, Hynix, and Micron. These are pin for pin compatible
replacement devices for one another. Table B.2 lists the recommended DDR SDRAM devices
B.2.3 DDR SDRAM Clock Signals
The DDR SDRAM clocks (DDR_CLK[2:0]) are driven by the iSNAP2110. In the reference
design, only two clock pairs are used DDR_CLK[2]P/N and DDR_CLK[0]P/N. The
DDR_CLK[2:0]P/N pairs must be designed taking into account the AC timing parameters. Refer
to Chapter 5 “Clocking and Timing” of the “iSNAP2110 Hardware Reference Manual” for details.
4. A memory array is a cluster of memory devices sharing the same chip select signal.
Table B.2 Recommended DDR SDRAM Devices
Manufacturer Device Organization Description Package Part Number
Samsung DDR SDRAM 16Mb x 16 256 Mb SSTL-2, DDR333@CL=2.5 TSOP-II 66 K4H5638F-TC/LB3
Hynix DDR SDRAM 16Mb x 16 256 Mb SSTL-2, DDR333@CL=2.5 TSOP-II 66 HY5DU561622DT-J
Micron DDR SDRAM 16Mb x 16 256 Mb SSTL-2, DDR333@CL=2.5 TSOP-II 66 MT46V16M16TG-6T
CS0_N
iSNAP2110
One Memory Array
ECC
DATA
DDR SDRAM
x16
DDR SDRAM
x16
4
32

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The following are the design recommendations (see Figure B.6):
Ensure that the clock phase at the feedback input is within ± 100ps of the phase at memory.
Keep the clocks away from the edge of the board and any connectors.
Traces should be routed with a minimum numbers of vias and no layer switching.
Each signal must have a reference layer with the following characteristics:
The GND plane(s) as first choice or the PWR plane(s) as a second choice.
No splits or discontinuities.
To allow best mutual coupling, signals pairs (positive and negative parts of a signal) should be
routed with the recommended distance, D (see Figure 4.2, “iSNAP2110 Reference Board
Stackup,” on page 15).
The placement of the parallel termination and its Vias must be placed in such a way that it
prevents the signals from being too far apart (see Figure B.6).
To avoid crosstalk, separate the clock signals from each other. The signals should be separated
from each other by a distance of S, which is at least three times the trace width (i.e., X ≥ 3W –
see Figure B.1)
Figure B.6 DDR SDRAM Routing Guidelines – Clock Signals
iSNAP Via
Clock Trace in an
inner layer (adjacent
to a GND plane)
Parallel
Termination Via
Memory Via
D - Recommended
Distance

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Figure B.7 DDR SDRAM Clock Topology
Note: DDR_CLK1_P/N is not used. The differential resistor should be placed at the junction of L1
and L2, which is the split point of the differential pair.
Segment L1 L2
Lengtha
1.25” 1.25”
Matching From pin to pin (L1+L2), each of the
four pin-pairs should be = the target
pin-pair ± 25 mils.
DDR SDRAM (ECC)
DDR SDRAM CLK #2
DDR SDRAM CLK #0
DDR SDRAM FB CLK
100
100Ω
iSNAP2110
L2
L2
L1
L1 L2
L2
Ω
L1
L1
L2
L2
L2
L2
DDR SDRAM
DDR SDRAM

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B.2.4 Address and Control Signals
The Address and Control lines (RAS, CAS, CS, WE, BA and CKE) should all be routed following
the same topology. Figure B.8 shows a typical address and control bit, each with 3 loads. Each
address and control bit goes to the center DDR SDRAM first.
Figure B.8 DDR SDRAM Address and Controls Topology
The following lists the rules/options for matching lengths for address and control bits:
Table B.3 shows the rules that apply for the portion of the topology ending at the center DDR
SDRAM device among the address and control signals.
Table B.4 shows the rules that apply for the two portions of the topology starting at the center
DDR SDRAM device going to the other two loads for each individual signal. .
Table B.3 DDR SDRAM Address and Controls Topology (ending at the center DDR SDRAM)
Segment L1 L11
Length a
0.5” 3.0”
Matching From pin to pin (L1+L11) one pin-pair should be =
the target pin-pair ±25 mils.
Table B.4 DDR SDRAM Address and Controls Topology - (starting at the center DDR SDRAM)
Segment L2
Length a
0.75" ≤ L2 ≤ 1.0"
Matching From pin to pin (L2) one pin-pair should be = the
target pin-pair ±25 mils
iSNAP2110
33Ω
DDR SDRAM
L2
L11L1
L2
DDR SDRAM
DDR SDRAM
See tables B.3, B.4, and B.5 for various options.

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Table B.5 shows the rules that apply for all 20 Address and Control bits, with one or more
loads .
B.2.5 Data, Data Strobe and Data Mask signals
Each byte of data (DQ[i]) and the ECC byte, the corresponding data strobe (DQS[n]) and mask
(DQM[n]) (Table B.6) should be routed together, with an inter-group5 matching of ± 500 mils and
intra-group matching of ± 50 mils. The overall length of any given byte should be between 1.5 and
2.5 inches (Figure B.9).
General layout considerations (see Figure B.9):
Traces should be routed with a minimum numbers of vias and no layer switching.
Each signal must have a reference layer with the following characteristics:
The GND plane(s) as first choice or the PWR plane(s) as a second choice.
No splits or discontinuities.
To avoid crosstalk, separate signals from each other. Signals should be separated from each
other by a distance of S, which is at least twice the trace width (i.e., S ≥ 2W – see Figure B.1).
Keep L1 as short as possible. The maximum allowed length is 500mils.
Table B.5 DDR SDRAM Address and Controls Topology (for all 20 Address and Control bits)
Segment L1 L11 L2
Length a
0.5" 3.0” 0.75" ≤ L2 ≤ 1.0"
Matching From pin to pin (L1+L11+L2) one pin-pair should be = the target
pin-pair ± 50 mils
5. Group (intra or inter) is defined as 8 data bits and the corresponding data strobe and data mask signals.
Table B.6 Data, Data Strobe, and Data Mask
DQ[i]
i = [n*8]:[(n*8) + 7]a
a. n = 0 to 3
DQS[n] DQM[n]
DQ[7:0] DQS[0] DQM[0]
DQ[15:8] DQS[1] DQM[1]
DQ[23:16] DQS[2] DQM[2]
DQ[31:24] DQS[3] DQM[3]
ECC-D [7:0] DQS[8] DQM[8]

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Control SRAM Interface Layout
Figure B.9 DDR SDRAM Data, Data Strobe, and Data Mask Topology
B.3 Control SRAM Interface Layout
The iSNAP2110 Control Memory SRAM interface provides clock, data, address and control
signals to the external SRAM memory. The iSNAP2110 provides two copies of the SRAM clock
on pins SRM_CLK and SRM_DUP_CLK. Each clock signals can be routed to a maximum of
four devices. Data is 72 bits wide and runs 2.5V I/O. There are 64 bits of data (SRM_D [63:0]),
and 8 bits of parity (SRM_DP [7:0]), to support data integrity. There are 20 bits of address on pins
SRM_A [19:0]. A shared pin, A20/SRM_CSn[3], may be used as SRM_A20 if SRM_CSn[3] is
not used. The four chip select outputs (SRM_CSn [3:0]), are active low. These pins allow
connection for up to four memory arrays (Figure B.10). The Write Enable, SRM_WEn, is active
low. There are eight SRAM byte write enable outputs (SRM_BWn[7:0]), which are also active
low.
Figure B.10 Example ZBT SRAM Memory Array
Segment L1 L2
Lengtha
a. All trace lengths are in inches.
0.5" 1.0" ≤ L2 ≤ 2.0"
Intra-Group matching Within a 10 bit
groupb
b. 8-Bits data + Strobe + Mask
From pin to pin (L1+L2), each of the 10 pin-pairs should
be = target pin-pair ±50 mils.
Inter-Group matching Among all the
10 bit groupsb.
From pin to pin (L1+L2), each of the 10 Bit groups should
be = the target pin-pair ±500 mils
iSNAP2110
Ω
L2L1
DDR SDRAM
33
CS0_N
iSNAP2110
One Memory Array
DATA + ECC ZBT SRAM
x36

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B.3.1 Address Signals
There are 20 bits of address on the 4.5 Mb devices with two pins reserved for future density
(address) expansion. These are the 20th and 21st bits on pins 43 (36 MB) and 42 (72 MB). These
bits may be left as no connects.
B.3.2 Control Signals
The pipelined ZBT SRAMs used have linear and interleaved burst mode capability. The interleaved
burst mode is not used in this design. The following synchronous control signals to the ZBT
SRAMs are all grounded: CKEn, CE2n and ADV/LD_N. The following asynchronous inputs are
also grounded: OEn, LBOn. CE2 is pulled high. Therefore, linear burst mode is used
continuously, clock is enabled continuously, new addresses are clocked immediately on the next
rising edge of the clock, and the output drivers are always enabled. The ZZ pin is connected to
GPIO[13], which is controlled by the iSNAP2110 when entering low power standby mode. The
CEn pin is always sampled immediately when a new address is clocked.
The iSNAP2110 SRAM Write Enable is active low and is connected to the R/Wn input on all the
SRAMs. When SRM_WEn is low, writes will occur on any bytes that have an active low
synchronous Byte Write Enable. The iSNAP2110 has eight SRAM byte write enable outputs,
which are active low. Each SRAM device has four Byte Write Enables and four corresponding data
bytes with parity bits. BWAn corresponds to DQA [7:0] and DQPA and so on through BWDn and
DQD [7:0] and DQPD.
B.3.3 Miscellaneous Signals
The SRAM manufacturer data sheet for connection of VDD, VDDQ, and VSS should be followed.
For some manufacturers, VDD pins, 14, 16, and 66, are mode pins, which should be connected to a
voltage of VIH or greater; these can be connected to VDD. For some manufacturers, these are NC
(not connected) pins.
B.3.4 SRAM Memory Devices
The choice of SRAM depth and width will affect the part count for the SRAM memory subsystem
design. This section covers the x36 width with one device per memory array. Since the iSNAP2110
is capable of supporting 4 memory array of SRAM by four chip select outputs, a single, dual or
quad memory array design is supported using either one, two, or four x36 devices.
Note: The iSNAP2110 does not prevent the designer from choosing other topologies, as the
principles used in the one device per memory array may be extended.
If 256 Kb x 36 (9 Mb) device is used, which yield 9 Mb per memory array. In a dual memory array
subsystem these devices will yield a total capacity of 18 Mb. In a quad memory array subsystem
these devices will yield a total capacity of 36 Mb. The SRAM devices used are 100 pin TQFP,
pipelined ZBT SRAMs available from companies such as Samsung and Cypress (Table B.7). These
are pin-for-pin compatible replacement devices for one another.

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Control SRAM Interface Layout
B.3.5 SRAM Layout Guidelines
These guidelines are specific to a single memory array (Figure B.10 on page 40) SRAM memory
subsystem with one clock. Figure B.11, Figure B.12, and Figure B.13 show the SRAM memory
signal constraints (clock, data, address and control, and chip select) between the iSNAP2110 and
the SRAM memory chips. The reason for the specification of the branch lengths and termination
values is due to the timing and signal integrity characteristics required for the SRAM interface to
function properly with the given memory components and physical layout.
B.3.6 SRAM Clock
The 125 MHz clock signal, SRM_CLK should be routed first and always adjacent to a GND plane
with a minimum of vias and matched trace length. When routing SRM_CLK, place the series
resistor as close as possible to the iSNAP2110. Then match the rest of the trace lengths to meet the
topology described in Figure B.11.
Note: SRM_DUP_CLK is not used.
Figure B.11 SRAM Clock Signal Topology
Table B.7 Recommended Control SRAM Devices
Manufacturer Device Description Package Part Number
Cypress ZBT SRAM 9 Mb 2.5V VDD, 2.5VDDQ, 200 MHz,
256 Kb x 36, pipelined
100 TQFP CY7C1354BV25-200AC
Samsung ZBT SRAM 9 Mb 2.5V VDD, 2.5VDDQ, 250 MHz,
256 Kb x 36, pipelined
100 TQFP K7N803649B-QC20
Segment L1 L2
Lengtha
0.25” 12.0”
33Ω
ZBT SRAM
iSNAP2110
L1 L2

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B.3.7 SRAM Data, Data Parity, and Byte Write Enable
The SRM_D [31:0], SRM_DP [3:0], and SRM_BW[3:0] are routed point-to-point. Lengths
should be matched to within ±50 mils (Figure B.12).
Figure B.12 SRAM Data, Data Parity, and Byte Write Enable Topology
B.3.8 SRAM Address and Control
The SRAM address signals SRM_A [19:0] and the Write enable signal SRM_WE_N should
match the Data and Chip Select signals lengths within ±50 mils. Each of these signals is connected
to one load (Figure B.13).
Figure B.13 SRAM Address and Control Signal Topology
Segment L1 L2a
a. Driver to receiver
Lengthb
b. All trace lengths are in inches
0.5” 2.0”
Matching From pin to pin (L1+L2) one pin-pair
should be = the target pin-pair ±50 mils
Segment L1
Lengtha
1.5”
Matching From pin to pin (L1) one pin-pair should be = the target pin-
pair ±50 mils
iSNAP2110
L2L1
ZBT SRAM
33Ω
iSNAP2110
L1
ZBT SRAM

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GPM Interface Layout
B.4 GPM Interface Layout
The iSNAP2110 GPM interface provides data, address, and control signals to the Flash.
B.4.1 Flash Interface
The Flash memory contains the default configuration parameters for the iSNAP2110, as well as
runtime GPP code. After reset, the iSNAP2110 starts accessing the flash to upload PCI-X register
definition values and initial values for other on-chip memory elements. The Flash occupies the
2 MB at CPM_CS0n memory bank. The Flash interface is 16-bit wide.
B.4.2 UART Daughter Card Connector Interface (Optional)
The UART daughter card connector on the iSNAP2110 Reference Board is optional. It connects to
a RS232 serial port interface. Only the GPM_D[7:0], GPM_A[2:0] and GPM_CS[3:2]_N are
routed to this connector.
B.4.3 GPM Flash Memory Device
A 1 Mb x16 (16 Mb) Flash memory device is used, which is equivalent to 2 MB. The Flash used is
a 48 pin TSOP-48 package from ATMEL. Table B.8 shows the recommended ATMEL Flash
device used with the iSNAP2110.
Table B.8 Recommended Flash Devicea
a. Flash Device is CFI compliant.
Manufacturer Device Description Package Part Number
ATMEL Flash 1 Mb x 16, 70 ns TSOP-48 AT49BV162A-70TI

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B.4.4 GPM Data and Data Parity
The GPM_D [15:0] should be routed as a one layer Tee (Figure B.14).
Figure B.14 GPM Data and Data Parity Signal Topology
B.4.5 GPM Address and Control
The GPM address signals GPM_A [19:0] and the enable signal GPM_WEn, GPM_OEn should
be matched to the data and chip select signals lengths. GPM_A [19:0] should be routed as a single
layer Tee, where GPM_A [2:0], has two loads (Flash and UART), and GPM_A [19:3] has one
load (Flash). The GPM_WEn and GPM_OEn signals are also routed as a single layered Tee with
two loads, Flash and UART connector. Place the series resistor as close to iSNAP as possible.
Figure B.15 and Figure B.16 shows two possible topologies for GPM address control.
Segment L1 L2
Lengtha
2.0" ≤ L1 ≤ 3.5" 0.5" ≤ L2 ≤ 1.0"
Matching From pin to pin (L1+L2) one
pin-pair should be = the
target pin-pair ±500 mils
N/A
iSNAP2110
L1
L2
UART (Optional)
Flash

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GPM Interface Layout
Figure B.15 GPM Address and Control Signal Topology – Option 1
Figure B.16 GPM Address and Control Signal Topology – Option 2
Note: The above trace lengths and matching applies to both option 1 and 2.
Segment L1 L2 L3
Lengtha
2.0" ≤ L1≤ 2.5" 0.5"≤ L2 ≤ 1.0" 0.5"≤ L2 ≤ 1.0"
Matching From pin to pin (L1+L2) one pin-pair should
be = the target pin-pair ±500 mils
N/A
2.5V
470 Ω
iSNAP2110
L1 L4L2
Option 1: Pull up strapping option =470 ohms
This applies to GPM_A[13]
StrapOptions
Option1
L3
Flash UART(Optional)
470 Ω
iSNAP2110
L1
This applies to GPM_A[12]
Option 2: Pull down strapping option =470 ohm
StrapOptions
Option2
L4L2 L3
Flash UART(Optional)

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B.5 RGMII Interface Layout
The GE interface is based on the RGMII standard. These are 4-bits of data and a clock, which work
at DDR speed. The data is latched on both the rising and the falling edges of the clock (either the
Tx or the Rx clock).
The RGMII interface consists of four independent segments: two Rx and two Tx ports. Each can be
routed independently as long as the length and tolerances stated below (“RGMII Receive” on
page 47 and “RGMII Transmit” on page 48) are followed.
Note: The PHY device should support RGMII, if not, external glue logic will be required.
B.5.1 RGMII Receive
For the Receive part of the RGMII, the routing length can be anything between 1.0" to 1.5", as long
as all the data and clock per port are kept the same length with a tolerance of ±25 mils (see
Figure B.17).
Figure B.17 RGMII Data/Clock ReceiveTopology
Segment L1
Lengtha
1.0" ≤ L1 ≤ 1.5"
Matching From pin to pin (L1) one pin-pair should be = the target pin-pair ±25 mils
iSNAP2110
L1
PHY

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RGMII Interface Layout
B.5.2 RGMII Transmit
For the Transmit part of the RGMII, the routing length can be anything between 1.2" to 1.8", as
long as all the data and clock per port are kept the same length with a tolerance of ±25 mils
(Figure B.18).
Figure B.18 RGMII Data/Clock Transmit Topology
B.5.3 PCI(X)
The iSNAP2110 PCI/PCI-X interface is both PCI 2.3 and PCI-X 1.0a compliant. Please refer to the
PCI specifications for further details.
Segment L1
Lengtha
1.2” ≤ L1 ≤ 1.8”
Matching From pin to pin (L1) one pin-pair should be = the target pin-pair ±25 mils.
iSNAP2110
L1
PHY

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APPENDIX C: Optional Configuration
The various types of memories on the iSNAP2110 Reference Board are Double Data Rate (DDR)
SDRAM, SRAM and Flash, with different stuff options. Various Reference Board stuff options are:
Full width DDR SDRAM/SRAM or Half width DDR SDRAM/SRAM memories. The memory
stuff options for DDR SDRAM and SRAM are independent of each other.
Note: The “Full Width” configuration requires a minimum of two more memory components and
offers 220K IOPS across the two ports. The “Half Width” configuration can fit into a more
compact Low Profile PCI footprint with less components and a lower BOM.
SDRAM
The external SDRAM serves as a data buffer for receive packets. The SDRAM also stores
connection/context information and control block data used for communications between the
iSNAP2110 and the Host system.
Full-width: SDRAM memory supports a minimum of 128 MB and a maximum of 256 MB
memory size. The full memory data bus width is 72-bits of data and ECC that ensures data
integrity.
Half-width: SDRAM option supports a minimum of 64 MB and a maximum of 128 MB
memory size. The half memory data bus width is 36-bits of data and ECC.
SRAM
The SRAM is controlled by the Event/Queue Manager (E/QMgr) and is used to store the
iSNAP2110 internal data structures. The SRAM type is Zero Bus Turnaround (ZBT).
Full-width: SRAM memory supports a minimum of 2 MB and a maximum of 4 MB. The full
memory data bus width is 72-bits of data and ECC that ensures data integrity.
Half-width: SRAM memory supports a minimum of 1 MB and a maximum of 2 MB memory
size. The half memory data bus width is 36-bits of data and ECC.
Table C.1 lists the memory requirements for HBA.
Table C.1 HBA Memory Requirement
Memory type
Full width mode Half width Mode
Min Max Min Max
SDRAM 128 MB 256 MB 64 MB 128 MB
SRAM 2 MB 4 MB 1 MB 2 MB
Flash 1 MB 2 MB 1 MB 2 MB

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Flash
The Flash memory device interfaces to the iSNAP2110 through the General Purpose Processor
(GPP) and is used to store configuration parameters and runtime GPP code for the iSNAP2110. It
is also used to upload PCI-X register definition values and initial values for all functional elements
in the iSNAP2110 (PNs, Registers, and Flexible Logic Engine architecture (FLE)). The minimum
required Flash size is 1MB.

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Silverback Systems Confidential 51
Glossary
- A -
ACK TCP or iSCSI Acknowledge command
ADM Receive Admission (obsolete term, usually used in conjunction with RxADM -- see “Classification
Engine Rx”)
AHS Additional Header Segment – A variable-length header that optionally follows the 48-byte Basic
Header Segment in an iSCSI packet.
API Application Programming Interface
ARP Address Resolution Protocol
ASQ Application Stream Queue
ASF Alert Standard Format – Defines interfaces that provide access and manageability in OS-absent
environments
- B -
BHS Basic Header Segment
BIST Built-In Self Test
Block ID ID passed to the Control Bus to identify a specific module for register access. (Only required for
Event Queue Manager registers.)
Broadcast A transmission from one sender to all receivers
BSD Berkeley Software Distribution
- C -
CIFS Common Internet FIle System (Windows NT environment standard); Format for accessing and
storing data; runs over TCP/IP.
CID Connection Invariant Data – packet header information that is constant across all frames for a
particular connection (e.g., IP source and destination addresses).
CLI Command Line Interface
Command Descriptor
Block (CDB)
The standard format for SCSI commands. CDBs are commonly 6, 10, or 12 bytes long, though
they can be 16 bytes or of variable length.
Command Sequence Sequence of Encapsulation Engine Tx (akaTxSYN) bytes (describes a portion of a packet).
Command Stream Sequence of Encapsulation Engine Tx (aka TxSYN) transmission bytes.
Completion Entry An entry returned by a Completion Notification in the Completion Queue of the Queue Set used
to send a command to the iSNAP; contains Status (S) bits which indicate if an error was present
in the original command.
Completion Item
Descriptor
A Queue Set entry on a Completion Queue
Completion
Notification
A 16-byte entry in a Completion Queue indicating that a transaction is complete and no exception
information is present
Completion Queue Used to send Completion Notifications from the iSNAP to the Host. (Part of a Queue Set that also
contains a Work Queue.)

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52 SIlverback Systems Confidential
Context A structure which describes an abstract functional element of the system such as a TCP stream
or an iSCSI session.
Context ID The ID of a structure which describes an abstract functional element of the system such a TCP
stream or an iSCSI session
Control Hub Performs register reads and writes to modules within the iSNAP
Control Plane Maintains the Process Control Block (PCB) for the TCP connection
CPB Connection Parameter Block
CP-ULP Critical Path and Upper Layer Protocol processing.
CRC Cyclic Redundancy Check – detects data transmission errors; see CRC Manager
CRC Manager Manages the CRC function
- D -
DAFS Direct Access File System. Another format for rmote file I/O. Intendd to be much more efficient
that CIFS.
DAS Direct Attach Storage – Storage connected directly to the compute platform.
DDR-DRAM Double Data Rate DRAM
DDR-SDRAM Double Data Rate Syncronous DRAM – supports data transfer on both edges of each clock cycle
DDR-SSRAM Double Data Rate Synchronous SRAM
Device ID Code assigned to a specific device by a vendor. The Device ID for the iSNAP2100 is 0x2100 (big
endian).
DFM Design for Manufacture
DFT Design for Test
Direct Address 32-bit physical address in iSNAP2100 memory.
DIrect Data
Placement
Data transfer directly into the host application memory space (eliminates time consuming
memory copy operations and improves system performance)
DMA Direct Memory Access
DRAM Dynamic Random Access Memory
- E -
ECC Error correcting code
EEPROM Electrically eraseable programmable read only memory
EJTAG Enhanced JTAG
EO Execution Object. Classification (Rx) to Event/Queue Manager communication structure.
EPROM Eraseable programmable read only memory
ER Error Recovery
Execution Object See “EO”
- F -
FC Fibre Channel
FFL Firmware Foundation Layer – abstraction layer software between upper layer applications and
the hardware
FLE Flexible Logic Engine – programmable nanoprocessors which can be set to perform a variety of
tasks depending on the instructions in the local control store
FLEA Flexible Logic Engine Architecture
FLID Free List ID

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Free List A collection of MODs used for managing the allocation and deallocation of MODs and MOs
FUB Functional Unit Bus (iSCSI)
- G -
GB Gigabyte (2 to the 30th power or l,073,741,824 bytes. One gigabyte is equal to 1.024
megabytes.)
GE Gigabit Ethernet
GMAC Gigabit Ethernet Media Access Controller – transmits and receives data to/from the GMII
interface
Gpbs Gigabits per second, a data transfer speed measurement for high-speed networks such as
Gigabit Ethernet (a gigabit equals 1,000,000,000 bits).
GPCS Gigabit Physical Coding Sublayer – encodes and decodes the GMII interface for fiber channel.
GPM General Purpose Memory
GPP General Purpose Processor – one located on iSNAP2100
- H -
HBA Host Bus Adapter; a hardware card that plugs into a computer and provides a specific interface.
The term HBA is commonly used for SCSI adapters and Fibre Channel adapters. Ethernet
adapters are called network interface controllers (NICs).
HCC Host Command Controller (abbreviated HCCTL or HCC)
Header Data Splitting Separating the data and header information in a network packet and directing the information to a
specific location in Host memory space.
Host Address A 32-bit or 64-bit address in the PCI or PCI-X bus space
Host Command
Descriptor
Consists of both a Work Item Descriptor (WID) and an Work Item.
Host Descriptor A command block the host sends to the iSNAP that contains detailed iSNAP2100 command
instructions.
HQ Host Queue
HQS Host Queue Set
- I -
IB Interface Buffer – interface buffer mechanism within the WID interconnect
ICB Interconnect Control Buffer – the buffer interface on an interconnect port. The ICB provides a
decoupling between the interconnect internal and port external structure
ICC iSCSI Command Context – the internal representation of a SCSI command in local DRAM. An
ICC is a superset of a CDB and allows chaining and references to associated data structures
ICMP Internet Control Message Protocol
ICT In-Circuit Test
IF Interface
Index Cardinal instantiation of a structure in memory.
Initiator The originating end of a SCSI conversation (the device that requests data). Typically a controlling
device such as a server or workstation. See also "Target."
INTCX Interconnect
IOCTLs I/O Control – service calls which are included in Core Services and which are used for bootup
and configuration of the iSNAP device
IP Internet Protocol

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IP CP The IP Control Plane component in the Host drive; consists of ARP, Route Entity, and ICMP
Entity
IP SAN Same concpet as SAN except that the communication mechanism is Internet Protocol.
IP Storage Storage devices that use Internet Protocol to transport their data.
iSCSI Internet SCSI (Small Computer System Interface), an IP-based storage networking standard for
linking data storage facilities. (Parallel SCSI protocol mapped onto Internet Protocol.)
iSCSI CBD Command Descriptor Block (CBD) used to communicate with the iSNAP 2100 iSCSI service via
the Host Interface (see “Command Descriptor Block”).
iSCSI CP The iSCSI Control Plane component in the Host driver; maintains local iSCSI identity and
capabilities, a list of all iSCSI sessions on this system, and the identity of the remote partner for
each session
iSCSI DP iSCSI Data Plane; an upper layer data plane responsible for using the TCP byte stream to send
and receive iSCSI PDUs efficiently
iSCSI Interface
Queue
Used to send and receive all iSCSI and TCP connection management messages for those
connections in use for iSCSI and off-loaded to the iSNAP2100
ISID Initiator Session Identifier; a 48-bit number, generated by the initiator, that uniquely identifies a
session between the initiator and the target. This value is created during the login process, and is
sent to the target with a Login PDU.
iSNS Internet Storage Name Server; a lightweight discovery protocol that can be deployed in
centralized iSNS servers, IP storage switches, and target devices. The name registration service
enables IP storage devices to register their attributes and address, analogous to the Fibre
Channel SNS. Can reside anywhere within the IP network.
ITT Initiator Task Tag – assigned by initiator to each iSCSI task that it issues. While a task exists,this
tag must uniquely identify it session-wide.
I2
C Inter-IC – A multi-master bus, which means that multiple chips can be connected to the same bus
and each one can act as a master by initiating a data transfer.
- J -
JTAG Joint Test Action Group of the IEEE
- K -
- L -
LED Light Emitted Diode
Link Layer Interface
Queue
Used to send and receive Link Layer packets
LL Link Layer
LU Logical Unit
LUN Logical Unit Number; technically, the LUN is the number that identifies a sub-element within a
SCSI target device. In common usage, LUN is used to refer to the device itself, although LU
(Logical Unit) is the more proper term.
LUT Look Up Table
- M -
MAC or MAC Layer Media Access Controller or Media Access Control Layer. Responsible for moving data packets
across a shared channel.
Mb or Mbit Megabit

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MB or MByte Megabyte
Memory Object A block in DRAM
MO Memory Object – buffer in DRAM or host memory. May contain packet data or context
information; may also be customized by the customer for other data storage use.
MOD Memory Object Descriptor – a structure that maintains reference to a memory object as well as to
information specific to and associated with the object
MIB Management Information Base – list of status and count event statistics maintained for both
transmit and receive
MII Management Media Independent Interface Management
MMA
MSI Message Signaled Interrupts. A system performance enchancement that allows status messages
to be posed to a host without a system interrupt.
Multicast A broadcast message from one sender to many receivers.
- N -
NAS Network Attached Storage. A storage device that is attached to a LAN and provides file-oriented
storage to clients. Data is transferred in file formats (FIFS, NFS are common file formats).
NDMP Network Data Managment Protocol. Initially developed to facilitate tape backup operations over
IP.
NFS Network File System. Allows all network users to access shared files stored on computers of
different types. (Format for accessing/storing data across network created by SUN – widely
used).
NIC Network interface controller
NOP No Operation A command given to the CPU that causes nothing to happen. Sometimes used as
a tool to control timing-sensitive tasks.
NP Node Processor
- O -
Object ID See “Index”
OLTP Online transaction processing. The request and delivery of data betwen an Initiator (server) and
Target (disk) in a real-time environment.
OQ Object Queue
- P -
PB Parameter Block
PCB Process Control Block; an existing component of all TCP/IP implementations; a data structure
that maintains the state of a TCP connection and its relationship with other structures
PCI Peripheral Component Interface – A local 32 or 64-bit bus that runs at speeds depending on the
version. PCI-x buses are 64 bits and run at up to 133 MHz.
PDU Protocol Data Unit
PER PN Execution Request
PET Packet Event Trap protocol
PHY Physical Layer
PIO Peripheral Input/Output command
PN Processor (or Programming) Node – four Processor Nodes are located on the iSNAP chip
PNC Processor (or Programming) Node Controller

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Primitive A PCI register that controls the operation of a Queue Set
PROM Programmable Read Only Memory
Protocol Machine Provides all TCP capability, including reliable delivery of all bytes (through acknowledgement and
retransmission mechanisms such as timers), avoidance of network congestion (through back-off
mechanisms), re-assembly of packets received out of order.
PWM Pulse Width Modulation
- Q -
QSCB Queue Set Control Block
Queue List of linked or unlinked objects.
Queue Descriptor A structure that fully defines and describes a Queue
Queue Length The maximum valid value an index pointer into the queue can assume, and equals [(Queue
Size)-1]. Entries of Queue size N are mapped to index values [0,..., N-1] or [,.., (queue length)].
See Queue Size.
Queue Set A pair of queues comprised of a Work Queue and its associated Completion Queue
Queue Set Entry The structure of a Work Queue and Completion Queue
Queue Set Control
Block
A data structure that fully describes a Queue Set (one Work Queue and one Completion Queue);
records Producer/Consumer Pointers for the Queue Set; and defines placement of the Queue
Set within Host memory.
Queue Set ID A unique value that identifies a specific Queue Set.
Queue Size The size of a Work Queue or a Completion Queue measured in number of entries. See Queue
Length.
- R -
R2T Request to Transmit confirmation – SCSI response to a request to send command. The SCSI
initiator waits for an R2T from the target before sending the data OR
Ready to Transfer. R2T is sent by target when it is ready to receive data.
RAID Redundant Array of Independent Disks
RAM Random Access Memory
RCMP Remote Management Control Protocol
RDMA Remote Direct Memory Access – Mechanisms for fast, low latency data transfers between
remote CPUs typically separated over a LAN.
RGMII Reduced Gigabit Media Independent Interface
ROM Read Only Memory
RPC Remote Process Communication – A mechanism that allows different Hosts to communicate with
each other. (Widely used and similarly to IPC (Interprocessor Communication).)
- S -
SAN Storage Area Network – a storage network dedicated to storage traffic exclusively. A network of
host computers and mass storage devices. Used to share disks and tapes with multiple hosts.
Data is accessed in block mode.
SCSI Small Computer Serial Interface
SDI Serial Debugging Interface
SDRAM Synchronous DRAM
SM Session Management (or Manager) (iSCSI)
SMP Symmetric Multiprocessing

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SN Sequence Number (iSCSI)
SNAP Storage Network Access Processor
SNIA Storage Networking Industry Association
SPI-3 System Packet Interface Level 3
SPI-POS SPI Packet Over SONET
SRAM Static Random Access Memory
SSRAM Synchronous SRAM
Stream A memory abstraction structure that provides a continuous stream of bytes
Stream Address A specific data stream address from which data can be read
Streaming Interface SPI-3 serial I/O interface
Summary Descriptor A Queue Set entry on a Summary Queue.
Summary Item A 4-byte entry in a Summary Queue.
Summary Queue A special queue used in conjunction with the Interrupt mechanism to identify which Queue Sets
contain Completion Notifications.
Sum QID Summary Queue ID
SMBus System Management Bus – A two-wire interface through which various system
component chips can communicate with each other and with the rest of the system. It is based
on the principles of I2C.
- T -
TAP Test Access Port
Target The receiving end of a SCSI conversation, typically a device such as a disk drive, tape drive, or
scanner. See also "Initiator."
TBI Ten Bit Interface
TCP Transmission Control Protocol
TCP CP The TCP Control Plane component in the Host drive
TLV Time-Length-Value – Encoding method used for encoding optional parameters passed between
the Host and iSNAP. Used by the TCP Interface.
TM Task Management
TOE TCP/IP Offload Engine – a piece of hardware that implements the TCP/IP stack, and thereby
"offloads" this task from the main processor. Accelerates TCP protocol in special purpose
hardware. There are two types: Partial Offload, which typically handles only the Fast Path, in
order packets; and Full Offload, which manages out-of-order and missing packets. (This
hardware may be a custom ASIC or a network processor with firmware.)
TSID Target Session Identifier, a 16-bit number, generated by the target, that uniquely identifies a
session between the initiator and the target. This value is created during the login process, and is
sent to the initiator with a Login Response PDU.
TTC TCP Timing Controller
TTQ TCP Transmit Queue
TTT Target Transfer Tag (iSCSI)
- U -
UART Universal asynchronous receiver transmitter
UDP User Datagram Protocol – runs on top of IP networks (direct method for broadcasting messages)
ULP Upper Layer Protocol

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UTP Unshielded Twisted Pair
- V -
Vendor ID Code assigned to the vendor who created the device.
VFS Virtual File System
Virtualization Automation of functions in the storage infrastructure that simplifies the management and
operation of storage devices.
VI Virtual Interface – A low latency, high bandwidth protocol that allows different hosts to
communicate with each other.
VLAN Virtual LAN (IEEE 802.1Q/p) – allows stations on disparate networks to appear as if they are all
members of the same LAN
- W -
WIE Work Item Entry – same as a WID
Work Item (WI) The Work Item describes the service the Host requests of the iSNAP and the parameters for the
service request. The last 8 bytes of the WI contain the Base Address and Length to which the
WID points.
Work Item Descriptor
(WID)
A 16-byte Queue Set entry in a Work Queue sent to the iSNAP. Contains the iSNAP data
structures exchanged between the Host and the iSNAP. Includes a pointer to the last 8 bytes of
the Work Item.
Work Queue Used to send requests from the Host to the iSNAP; contains a WID of 16 bytes with a pointer to a
Work Item.
- X -
XTR Designator for iSNAP in the iSNAP code.
-Y-
- Z -
ZBT Zero Bus Turnaround (133 MHz)

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Index
A
Activity indication 5
AK29 pin 12
B
Bill of materials 27
BIST LED 5
Board interfaces 7
boundary-scan chain 12
bracket 16
C
Circuit areas 6
Circuitry and routing 21
Configuration options 26
Connector
PCI 11
Context buffer memory 5
Control memory 5
Control SRAM 9
D
DDR SDRAM 8
Dimensions 2, 14
E
Ethernet interface 7
F
Features 5
Flash memory 5
Form factor 11
G
GE interface pin assignments 16
Gigabit ethernet interface 7
H
Hardware specifications 6
Height 2
I
I/O voltage 11
input clock 21
iSNAP2110
processor. 2
system development kit 2
J
JTAG 5
JTAG test mode 12
JTAG_MOD 12
JTG_TCK 12
JTG_TMS 12
JTG_TRSTn 12
L
LED indicator 5, 25
activity 25
GPIO 25
link 25
Length 2
Link indication 5
link status LEDs 26
M
Maximum heights 14
Memory interface
DDR SDRAM (Global Memory) 8
Flash (general purpose memory) 10
GPM 10
ZBT SRAM (control memory) 9
Multifunction support 5
O
onboard memory 5
Operating temperature 2
operational status 25
output clock 22

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60 Silverback SystemsConfidential iSNAP®2110 Reference Board Design Guide
P
PCI
connector 11
frequencies 11
interface 11
multi-function 12
physical characteristics 14
pin-pair 32
target pin-pair 32
Ports
Ethernet 5
Power
consumption 2
Product overview 2
R
Related publications 2
RGMII 5
RJ-45 connectors 7
S
System requirements 2
T
target pin-pair 32
target-pin-pair
delta 32
group of pin-pairs 32
tolerance 32
TD0 12
TD1 12
V
Voltage
Supply 11

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