1. ARM Cortex-M0 The 8 / 32-Bit Difference
August 20, 2012 Paul Nickelsberg Orchid Technologies Engineering and Consulting, Inc.

2. Venerable 8-Bit Micros Intel 8080 / Intel 8085 Zilog Z80
Hitachi 64C180
Intel 8051
Intel 8048
Motorola 68HC05
Microchip PIC5

3. Historical Perspective
8-Bit Processor Design was a solution to the Size / Width / Time Question of the 1980’s
8-Bit Processor Design Balanced Size / Width / Time
Transistor Size
Instruction Sequence
Data Width

4. Historical Perspective
Clock
8-Bit Data
Time
Byte 1
Byte 2
Byte 3
Byte 4
More Time, Less Width

5. Historical Perspective
CPU
Main Memory
Fetch Instruction
Fetch Instruction
Read Data
Fetch Instruction
Fetch Instruction
Write Data
Time
Write Data
Write Data
Write Data
Fetch Instruction
Read Data

6. Historical Perspectives
Non-symmetric Processor Features
HL Register and 16-Bit Pointers (Special Purpose Registers)
Memory Page Registers
Common Memory, Banked Memory
Segment Registers
I/O Space Different from Memory Space
Maximum Memory Size Limits of Addresses
Compiler Models – Tiny, Small, Medium, Large, Huge

7. What has changed? Feature Size Approx Year Processors 10 µm 1971
Intel 4004, 8008
3 µm
1975
Intel 8085, 8088
1.5 µm
1982
Intel 80286
1 µm
1985
Intel 80386
800 nm
1989
Intel 80486
600 nm
1994
350 nm
1995
Intel Pentium
250 nm
1998
Intel Pentium II
180 nm
1999
130 nm
2000
Intel Pentium IV
90 nm
2002
Intel Celeron
65 nm
2006
Intel Xeon

8. Credit Wikipedia
From 3µm to 90nm in 30 Years

9. Low Cost 32-Bit Computing
32-Bit Processor Design was a solution to the Size / Width / Time Question of the 2000’s
32-Bit Processor Design Re-balances Size / Width / Time
Transistor Size
Instruction Sequence
Data Width

10. Low Cost 32-Bit Computing
Clock
8-Bit Data
Time
Byte 1
Byte 2
Byte 3
Byte 4
More Time, Less Width
Clock
32-Bit Data
Time
Dword
Less Time, More Width

11. 32-Bit Computing Examples
Timer Example
Shift Register Example
Adder Example
Multiplier Example

12. Timer Example Using an 8MHz Input Clock, Create a 10mSec Timer
8-Bit Approach, Counts 0x using three chained timers
32-Bit Approach, Counts 0x using a single timer
8-Bit Timer
32-Bit Timer
8-Bit Timer
8-Bit Timer

13. Shift Register Example
Decode a 29-bit Serial Input Word
Shift Input
Carry Out
Carry Out
Carry Out
Shift Input
Byte 1
Byte 2
Byte 3
Byte 4
32-Bit Register
compare
compare
compare
compare
compare
AND
Far less ‘house-keeping’
8-Bit Approach, A lot of Steps
32-Bit Approach, Fewer Steps

14. Adder Example Add two 32-bit numbers A + B = C
Byte 4A
32 Bit Value A
Byte 4B
32 Bit Value B
Byte 3A
32 Bit Value C
carry
Byte 3B
Byte 2A
carry
Byte 2B
Byte 1A
carry
Byte 1B
Byte 1C
Byte 2C
Byte 3C
Byte 4C
8-Bit Approach, A lot of Steps
32-Bit Approach, Fewer Steps

15. Multiplier Example Multiply two 32-bit numbers A x B = C
MOV A, XL MOV B, YL
MUL AB
MOV R0, A
MOV R1, B
MOV A, XL
MOV B, YH
ADD A, R1
MOV R1, A
MOV A, B
ADDC A, #0
MOV R2, A
MOV A, XH
MOV B, YL
MOV R1, A
MOV A, B
ADDC A, R2
MOV R2, A
MOV A, XH
MOV B, YH
MUL AB
ADD A, R2
ADDC A, #0
MOV R3, A
MULS r0, r1, r0
8-Bit Approach, A lot of Steps
32-Bit Approach, Fewer Steps

16. Bonus, ARCTAN Example! y MORE ON THIS LATER angle MORE ON THIS LATER x
Find the angle with tangent y/x
8-Bit Approach 12MHz
32-Bit Approach 12MHz

17. ARM Cortex-M0 Features Clocking Mgnt Power Monitor
SCB
SYSTICK
Clocking Mgnt Power Monitor
Reset Manager Fast GPIO
USB Interface
CAN Interface
DMA Channels
A/D Conversion
Multiple Timers
Flash Memory
Smart Card
Real Time Clock
I2C Interface
SPI Interface
UART Interface
SWD Debug
Unique ID
CRC Calculator
ROM API
Static Memory
Nested Vector Interrupt Controller
32 Bit CPU
AHB Lite
Debug Access