1. Kenyon Tsai
2016.06.22
An overview of PCI Express Physical Layer
Technology

2. ASMedia Confidential DocumentASMedia Confidential Document
Introduction

3. ASMedia Confidential DocumentASMedia Confidential Document
Introduction
 Lane count : x1, x2, x4, x8, x12, x16 and x32
 Rate :
Raw bit rate Link BW
PCIe 1.x 2.5 Gigabits/s 2 Gb/s
PCIe 2.x 5 Gigabits/s 4 Gb/s
PCIe 3.x 8 Gigabits/s ~8 Gb/s
PCIe 4 16 Gigabits/s ~16 Gb/s

4. ASMedia Confidential DocumentASMedia Confidential Document
PCIe Layering Overview
 There are three discrete logical layers
 Transaction Layer
 Data Link Layer
 Physical Layer

5. ASMedia Confidential DocumentASMedia Confidential Document
Physical Layer
 The Physical Layer is divided into two blocks
 Logical sub-blocks
 Electrical sub-blocks
Physical Layer
Logical sub-blocks
Electrical sub-blocks

6. ASMedia Confidential DocumentASMedia Confidential Document
8b/10b encoding
 Purpose of 8b/10b encoding
 To achieve DC-balance
 Provide enough state changes to allow reasonable clock recovery

7. ASMedia Confidential DocumentASMedia Confidential Document
Data Scrambling
 Purposes of scrambling
 For energy dispersal on the carrier
 Reducing inter-carrier signal interference

8. ASMedia Confidential DocumentASMedia Confidential Document
De-emphasis
 Definition of De-emphasis

9. ASMedia Confidential DocumentASMedia Confidential Document
De-emphasis
 Purposes of De-emphasis
 To compensate Inter-symbol interference

10. ASMedia Confidential DocumentASMedia Confidential Document
De-emphasis
 Purposes of De-emphasis
 To compensate Inter-symbol interference

11. ASMedia Confidential DocumentASMedia Confidential Document
Link training
 Training Does
 Link data rate negotiation
 Bit lock per Lane
 Lane polarity
 Symbol lock per Lane
 Lane ordering within a Link
 Link width negotiation
 Lane-to-Lane de-skew within a multi-Lane Link

12. ASMedia Confidential DocumentASMedia Confidential Document
Link training
 Link Training and Status State Machine (LTSSM) Descriptions

13. ASMedia Confidential DocumentASMedia Confidential Document
Link training - Detect
 To detect when a far end termination is present

14. ASMedia Confidential DocumentASMedia Confidential Document
Thanks