arm introduction

1. A
PRESENTATION
BY
EDUTECHLEARNERS
ARM
Advance RISC Machine
http://www.edutechlearners.com

2. ARM Application
Apple iPod
Nano Ford Sync In-Car Comm &
Entertainment System
Sony Playstation 3
(60GB)
Nokia N93

3. ARM Partenship

4. ARM Advantage

5. Why ARM ???
ARM is one of the most licensed and
thus widespread processor cores in the
world.
Used especially in portable devices due
to low power consumption and
reasonable performance
Several interesting extension available
like THUMB instruction set and
Jazelle Java Machine

6. Computer Architecture
Describes Users View of the Computer
Eg.
Instruction Set
Visible Registers
Memory Management Table Structure
Exception Handling Models etc.

7. Computer Organization
Describes User Invisible
Implementation of the Architecture
Eg.
Pipeline Struture
Transparent Cache
Translation Look Aside Buffers etc

8. RISC vs. CISC Architecture
RISC CISC
Fixed width Instructions Variable length instructions
Few Formats of Instructions Several formats of instructions
Load/Store Architecture Memory Values can be used as operands in
instructions
Large Register Banks Small Register Bank
Instructions are pipelinable Pipelining is complex
Single Cycle execution of all instructions Multi cycle execution on instructions

9. RISC Advantages
A small Die Size
A Shorter Development Time
Higher Performance
Smaller things have higher natural
frequencies.

10. RISC Disadvantages
Generally poor code density (Fixed
Length Instruction)

11. ARM History
ARM – Acron RISC Machine(1983-1985)
Acron Computers Limited ,Cambridge,
England.
ARM – Advanced RISC Machine 1990
ARM Limited ,1990
ARM has been licensed to many
semiconductor manufacturers

12. Architecture Revisions
1998 2000 2002 2004
time
version
ARMv5
ARMv6
1994 1996 2006
V4
StrongARM® ARM926EJ-S™
XScaleTM
ARM102xE ARM1026EJ-S™
ARM9x6E
ARM92xT
ARM1136JF-S™
ARM7TDMI-S™
ARM720T™
XScale is a trademark of Intel Corporation
ARMv7
SC100™
SC200
™
ARM1176JZF-S™
ARM1156T2F-S™

13. Features used from RISC
A Load/Store Architecture
Fixed Length 32 bit Instructions
3-Address Instruction Formats

14. Load Store Architecture
Memory can be accessed only through two
dedicated instructions
LDR ; Move word from memory to register
STR ; Move word from register to memory
All other instructions have to work on
registers only

15. 3 Address Instruction Format
Function Dest. Addr. Op2 Addr. Op1 Addr.
f bits n bits n bits n bits
Example
Add d, s1, s2 ; d =s1+s2

16. Pipelining
Break instructions into steps
Work on instructions like in an assembly line
Allows for more instructions to be executed in
less time
A n-stage pipeline is n times faster than a non
pipeline processor (in theory)

17. MISC/RISC Pipeline Stages
Fetch instruction
Decode instruction
Execute instruction
Access operand
Write result
 Note: Slight variations depending on processor

18. Without Pipelining
Normally, you would peform the fetch, decode,
execute, operate, and write steps of an instruction
and then move on to the next instruction

19. Without Pipelining
Instr 1
Instr 2
Clock Cycle 1 2 3 4 5 6 7 8 9 10

20. With Pipelining
The processor is able to perform each stage
simultaneously.
If the processor is decoding an instruction, it may
also fetch another instruction at the same time.

21. With Pipelining
Clock Cycle 1 2 3 4 5 6 7 8 9
Instr 1
Instr 2
Instr 3
Instr 4
Instr 5

22. Pipeline (cont.)
Length of pipeline depends on the longest step
Thus in RISC, all instructions were made to be the
same length
Each stage takes 1 clock cycle
In theory, an instruction should be finished each
clock cycle

23. Pipeline changes for ARM9TDMI
Instruction
Fetch
Shift + ALU Memory
Access
Reg
Write
Reg
Read
Reg
Decode
FETCH DECODE EXECUTE MEMORY WRITE
ARM9TDMI
ARM or Thumb
Inst Decode
Reg Select
Reg
Read
Shift ALU Reg
Writ
e
Thumb→ Α
RM
decompress
ARM
decode
Instruction
Fetch
FETCH DECODE EXECUTE
ARM7TDMI

24. ARM10 vs. ARM11 Pipelines
ARM11
Fetch
1
Fetch
2
Decode Issue
Shift ALU Saturate
Write
back
MAC
1
MAC
2
MAC
3
Address
Data
Cache
1
Data
Cache
2
Shift + ALU
Memory
Access Reg
Write
FETCH DECODE EXECUTE MEMORY WRITE
Reg Read
Multiply
Branch
Prediction
Instruction
Fetch
ISSUE
ARM or
Thumb
Instruction
Decode Multipl
y Add
ARM10

25. ARM Design Policy
ARM core uses RISC Architecture
 Reduced Instruction Set
 Load Store Architecture
 Large No of General Purpose Registers.
 Parallel execution with Pipelines
But some differences from RISC
 Enhanced instructions for
 DSP instructions
 THUMB State
 Conditional Execution Instructions
 32 bit Barrel Shifter

26. Registers
ARM has Load Store Architecture
General Purpose Registers can hold
data or address
Total of 37 Registers each of 32 bit
There are 17 or 18 active registers
16 data registers
2 status registers

27. Registers
Registers R0-R12 are General Purpose
Registers
R13 is used as Stack Pointer(SP)
R14 is used as Link Register(LR)
R15 is used as Program Counter(PC)
CPSR is Current Program Status Register
SPSR is Saved Program Status Register
R0
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15

28. CPSR
N Z C V J U n d e f i n e d I F T M o d e
hold information about the most recently performed ALU operation
set the processor operating mode
• Condition code flags
– N = Negative result from ALU
– Z = Zero result from ALU
– C = ALU operation Carried
out
– V = ALU operation
overflowed
• Interrupt Disable bits.
– I = 1: Disables the IRQ.
– F = 1: Disables the FIQ.
• T Bit
– Architecture xT only
– T = 0: Processor in ARM
state
– T = 1: Processor in Thumb
state
• Mode bits
– Specify the processor mode
• J bit
– Architecture 5TEJ only
– J = 1: Processor in Jazelle
state

29. Operation Modes
Mode Registers CPSR[4:0]
User User 10000
FIQ _fiq 10001
IRQ _irq 10010
Supervisor Mode _svc 10011
Abort _abt 10111
Undefined
Instruction
_und 11011
System User 11111

30. Processor Modes

31. Processor Modes
Processor modes are execution modes which determines
active registers and privileges
List of Modes
 Abort
 Fast Interrupt
 Interrupt
 Supervisor
 System
 Undefined
 User
All except user mode are privileged
 User mode is for normal execution of programs and applications
 Privileged modes allow full Read/Write to CPSR.

32. Processor Modes
User Unprivileged mode for most applications
to run
FIQ Fast Interrupt Routine
IRQ Interrupt Request
Supervisor Entered on reset an when there is a exception
Abort Entered when data or instruction prefetch
aborted
Undefined When an undefined instructions is executed
System Privileged user mode for operating system

33. ARM Exceptions
ARM supports range of Interrupts,
Traps, Supervisor Calls, all grouped
under General Exceptions

34. Exceptions
Generated by internal and external events
Support 7 types of exceptions
 Reset - Only in Supervisor Mode
 Software Interrupt – in Supervisor Mode
 IRQ – on IRQ interrupt
 FIQ – on FIQ interrupt
 Data Abort – in Abort Mode
 Undefined Instruction – in Undefined Mode
 Prefetch Abort – in Abort Mode

35. Exception Priorities
1 Reset (Highest Priority)
2 Data Abort
3 FIQ
4 IRQ
5 Prefetch Abort
6 SWI,Undefined

36. ARM Processor
• ARM7 Family
– ARM7EJ-S
– ARM7TDMI
– ARM7TDMI-S
– ARM720T
• ARM9/9E Families
– ARM920T
– ARM922T
– ARM926EJ-S
– ARM940T
– ARM946E-S
– ARM966E-S
– ARM968E-S
• Vector Floating Point Families
– VFP10
• ARM10 Family
– ARM1020E
– ARM1022E
– ARM1026EJ-S
• ARM11 Family
- ARM1136J-S
- ARM1136JF-S
- ARM1156T2(F)-S
- ARM1176JZ(F)-S
- ARM11 MPCore
• Cortex Family
- Cortex-A8
- Cortex-M1
- Cortex-M3
- Cortex-R4
• Other Processors/ Microarchitectures
- StrongARM (DEC-Intel)
- Xscale (Intel- Marvell Tech)
- Other

37. ARM Processor Families
Naming Convention
ARM[x][y][z][T][D][M][I][E][J][F][S]
 X – Family
 Y - Memory management /protection
 Z – Cache
 T - Thumb Mode
 D – JTAG Debugging
 M – Multiplier
 I – Embedded ICE Macrocell
 E – Enhanced Instruction (implies TDMI)
 J – Jazelle hardware accelerated java
 F – Floating point unit
 S – Synthesizable Version

38. Instruction Set Architecture
Architecture Thumb DSP Jazelle TrustZone Thumb2
v4T *
v5TE * *
v5TEJ * * *
V6 * * * *
v6Z * * * * *
v6T2 * * * * *

39. Introduction to ARM7TDMI
Version 4
Von Neumann Architecture
 32 bit data bus
 Data size can be byte , half word or word
 Word : 4 bytes aligned
 Half Word : 2 byte aligned
Supports
 Thumb : 16 bit compressed instruction set
 Debug: On chip debug support
 Enhanced Multiply : Higher performance ,Long multiply
 Embedded ICE Hardware

40. Cortex Family
ARM Cortex family comprises three series, which
all implement the Thumb2 instruction set to
address the increasing demands of various
markets:
1 ARM Cortex – A Series: application processors
for complex OS and user applications
2 ARM Cortex – R Series : embedded processors
for real time systems
3 ARM Cortex – M Series : deeply embedded
processors optimized for cost sensitive
applications, as Mobile Devices.

41. Provide hardware support for two separate address
spaces i.e. code executing in the non secure world cannot
gain access to any address space marked as secure
A new mode ‘Secure Monitor’ within the core acts as a
gatekeeper and reliably switches the system between
secure and no secure states
Protection of on and off chip memory and peripherals
from software attack
Services such as network virus protection, m-commerce
transactions and the protection of user secrets such as
keys

42. Operating States
Supports 2 Instruction Sets
ARM – 32 bit instruction set
Thumb – 16 bit instruction set

43. Thumb State
Subset of the ARM instructions
Higher code density (35% reduction)
Better performance than 16 bit processors
Suitable for use with 16 bit memory
devices(160 % better performance)
Transparently decompressed to 32 bit
instructions

44. ARM State
Able to access more large memories
efficiently
32 bit integer arithmetic in a single
cycle
More number of instructions
Better performance

45. Switching States
ARM to Thumb
Execute the BX instruction with state
bit=1
Thumb to ARM
Execute the BX instruction with state
bit =0
An interrupt or exception cccurs

46. Which State to Use
Low memory system : use thumb
16 bit memory : use thumb
Performance is critical :use ARM
Example : in execution of interrupt
routines
Performance is critical and Memory is low :
use both ARM and thumb
Example : In interrupt routines

47. ARM Debug Architecture
ARM
core
ETM
TAP
controller
Trace Port
JTAG port
Ethernet
Debugger (+
optional
trace tools)
 EmbeddedICE Logic
 Provides breakpoints and processor/system
access
 JTAG interface (ICE)
 Converts debugger commands to JTAG signals
 Embedded trace Macrocell (ETM)
 Compresses real-time instruction and data access
trace
 Contains ICE features (trigger & filter logic)
 Trace port analyzer (TPA)
 Captures trace in a deep buffer
EmbeddedICE
Logic

48. Thanks…........