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ARM Ltd. Originally part of a government sponsored IT programme to provide computers in schoolsThe BBC' computer, Acorn, then Archimedes. ARM founded in November 1990Spun out of Acorn ComputersDesigns the ARM range of RISC processor coresLicenses ARM core designs to semiconductor partners who
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1. Introduction to ARM
Architecture, Programmers Model and Assembler Embedded Systems Programming
2. ARM Ltd Originally part of a government sponsored IT programme to provide computers in schools
The BBC computer, Acorn, then Archimedes.
ARM founded in November 1990
Spun out of Acorn Computers
Designs the ARM range of RISC processor cores
Licenses ARM core designs to semiconductor partners who fabricate and sell to their customers.
ARM does not fabricate silicon itself
Also develop technologies to assist with the design-in of the ARM architecture
Software tools, boards, debug hardware, application software, bus architectures, peripherals etc
3. Why ARM? ??Leading provider of 32-bit embedded RISC microprocessors
75% of market
??Common architecture
??High performance
??Low power consumption
??Low system cost
??Solutions for
Embedded real-time systems for mass storage, automotive, industrial and networking applications
Secure applications smartcards and SIMs
??Open platforms running complex operating systems
4. What is RISC? What is RISC
Reduced instructions fixed length
Use of pipelines to breakdown and speed up processing
Large number of registers used as very fast onboard RAM
Load-store architecture must load and store from memory to register via special instructions
Overall faster, simpler processer
5. ARM Architecture Based on the Berkeley RISC machine
Fixed length instructions
Pipe lines
Load/store architecture
The ARM is a 32-bit architecture.
When used in relation to the ARM:
Byte means 8 bits
Halfword means 16 bits (two bytes)
Word means 32 bits (four bytes)
Most ARMs implement two instruction sets
32-bit ARM Instruction Set
16-bit Thumb Instruction Set
Jazelle cores can also execute Java bytecode
6. ARM and RISC The ARM processors have many features in common with RISC chips but is not pure RISC
Uses variable cycle instructions
In-line barrel shifter leads to complex instructions
Thumb mode a 16 bit extension to ARM assembler
Conditional execution of instructions
Enhanced instructions ie DSP instructions
ARM processors are well adapted to embedded, low power and mobile solutions
7. Architecture Variants ARMv1
First version of ARM processor
26-bit addressing, no multiply / coprocessor
ARMv2
ARM2, First commercial chip
Included 32-bit result multiply instructions / coprocessor support
ARMv2a
ARM3 chip with on-chip cache
Added atomic load and store
Coprocessor 15 (cache management)
ARMv3
ARM6, first processor after being independent
32-bit addressing, separate CPSR, SPSR, virtual memory support
8. Architecture Variants ARMv4
added half- word load and store.
ARMv5
improved ARM and Thumb interworking, count leading- zeroes (CLZ) instruction, and architecture variants:
E enhanced DSP instructions including saturated arithmetic operations and 16- bit multiply operations
J support for new Java state, offering hardware and optimized software acceleration of bytecode execution.
ARMv6
Include TEJ enhancements Memory management, multiprocessing, SIMD instructions
6 new status bits (GE[3:0], E- , A- bits)
9. Memory Formats The ARM views memory as a linear collection of bytes numbered upwards from zero. Bytes 0 to 3 hold the first stored word, bytes 4 to 7 the second and so on. The ARM can treat words in memory as being stored either in Big Endian or Little Endian format.
A word is 32 bits
Addresses are 32 bits
10. Little endian addresses of bytes within words In little endian format, the lowest numbered byte in a word is considered the words least significant byte, and the highest numbered byte the most significant. Byte 0 of the memory system is therefore connected to data lines 7 through 0.
11. Big endian addresses of bytes within words In big endian format, the most significant byte of a word is stored at the lowest numbered byte and the least significant byte at the highest numbered byte. Byte 0 of the memory system is therefore connected to data lines 31 through 24.
12. ARM processor modes
13. The ARM register set
15. Program Status Register format In user programs only the top 4 bits of the CPSR are relevant
N - the result was negative
Z - the result was zero
C - the result produced a carry out
V - the result generated an arithmetic overflow
I, F interrupt enable bits
T instruction set (Thumb/ARM)
16. The CPSR mode bits
17. Exception processing modes
18. ARM 7 internals
19. The ARM instruction set a) Data processing instructions
b) Data transfer instructions
c) Control flow & conditional execution
d) Special instructions
20. Data processing instructions ALL operands are 32-bits wide and either:
come from registers, or are literals (immediate values ) specified in the instruction
The result, if any, is 32-bits wide and goes into a register
except long multiplies generate 64-bit results
All operand and result registers are specified independently