1. AVR CPU Core & 8 bit AVR Instruction Set

2. 안철수 KAIST 석좌교수 "개발자가 성공하는 길"

3. Block Diagram of the AVR Architecture

4. AVR Architecture Flash program memory (16bit) Data Memory (8 bit)
16 bit x 216 = 2 byte x 64 k = 128 kbyte
Program code가 저장되는 곳
Data Memory (8 bit)
범용 register : 32 byte
I/O register : 64 byte
Ext I/O register : 160 byte
SRAM : 4096byte
변수가 저장되는 곳
PC : Program Counter
address of the instruction being executed

5. Program / Compile / Execution
Program 작성 -> C code 생성
Compile -> hex code 생성
hex code : download 가 가능한 code
machine code (opcode) : 실행 가능한 code
assembly code : machine code의 의미
Execution
start address of program code => PC
Fetch : PC -> flash program memory => machine code -> IR
PC = PC+1 (또는 PC+2) (IR : instruction register)
Decode : instruction decode
Register Operand Fetch
ALU Operation Execute
Result Write Back
goto Fetch

6. Instruction Execution
an element of an executable program
a single operation of a processor
Parallel Instruction Fetches and Instruction Executions
Single Clock Cycle Execution : Harvard architecture
clkCPU : system clock
Atmega 128 : 16MHz 가능, XTAL1 pin으로 공급
실습 kit : MHz (확인요)

7. Single Cycle ALU Operation (in AVR)
Execution Cycle
Execution Time
1/clkCPU
clkCPU = 16 MHz ?
clkCPU = MHz ?

8. 8 bit AVR Instruction Set
Operation Code + Operand
Operation Code : ALU가 실행할 내용
Operand : ALU가 실행할 대상
Ex) ADC : Add with Carry
‘ADC R1, R2’ 의 opcode 는 ?

9. Operation Code의 유형 Arithmetic and Logic Branch Data Transfer
범용 레지스터간의 사칙연산과 로직 연산
ADC, AND, SUB, AND, OR, …
Branch
Change program counter : 다른 opcode위치로 이동
JMP, BRBC, …
Data Transfer
Load : SRAM등의 Data를 범용 Register로 이동 (LD, LDI, …)
Store : 범용 Register의 값을 SRAM 등으로 이동 (ST, STD, …)
Bit and Bit-Test
Register의 특정 bit을 set(=‘1’)하거나 clear(=‘0’)으로 변경
SBI, CLI, ….
MCU Control

10. Data Addressing Mode : Operand의 유형
Immediate
actual operand
Direct (absolute)
address of operand
Register Direct, I/O Direct, Data Direct
Indirect
Address that specifies (or points to ) operand
Data Indirect, Data Indirect with Displacement, Data Indirect with Pre-Decrement, Data Indirect with Post-Increment

11. Example) Immediate Addressing
ANDI – Logical AND with Immediate
ANDI r17, $0F

12. Example) Register Direct Addressing

13. Example) Register Direct Addressing
ADD – Add without Carry
ADD r1, r2
ADD r28, r28

14. Example) I/O Direct Addressing
IN - Load an I/O Location to Register
IN r25, $16

15. Example) Data Direct Addressing
LDS – Load Direct from Data Space
LDS R25, $0100
2 word/2 cycle

16. Data Indirect
X,Y,Z register 사용

17. Example) Data IndirectLD

18. Example) Data Indirect
CLR R27
LDI R26,$60
LD R0,X+
LD R1,X
LDI R26,$63
LD R2,X
LD R3,–X

19. Status Register
The Status Register contains information about the result of the most recently executed
SREG 비트 설명 I
Global Interrupt Enable T
Bit Copy Storage H
Half Carry Flag S
Sign Bit V
2's Complement Overflow Flag N
Negative Flag Z
Zero Flag C
Carry Flag

20. Status Register 비트 7(I : Global Interrupt Enable) :
전체 인터럽트를 허용하도록 설정하는 비트로 SEI 및 CLI 명령으로 이 비트를 제어할 수 있다.
비트 6(T : Bit Copy Storage) :
BLD, BST 명령을 사용하여 어느 레지스터의 한 비트 값의 복사 가능.
비트 5(H : Half Carry Flag) :
산술연산의 가감산에서 비트3에서 올림수가 발생하면 1로 세트 BCD 연산에 사용
비트 4(S : Sign Bit) :
플랙 N과 V의 XOR(eXclusive OR)값으로 정수들의 크기를 판단에 사용.

21. Status Register 비트 3(V : 2's Complement Overflow Flag) :
2의 보수 연산에서 오버플로우를 표시한다.
비트 2(N : Negative Flag) :
연산 결과값의 최상위 비트가 1로 되어 2의 수 표현을 사용하는 경우 연산 결과가 음수임을 표시.
비트 1(Z : Zero Flag) :
연산 결과값이 0이 되었음을 표시.
비트 0(C : Carry Flag) :
연산으로 자리올림이나 자리내림이 발생하면 1로 세트 된다.

22. Status Register
모든 연산이 실행된 후에 SREG이 변경됨
예) ADD

23. ★ JTAG Emulator JTAG (Joint Test Action Group)
Testing PCBs by using the JTAG Boundary-scan capability
Programming the non-volatile memories, Fuses and Lock bits
On-chip debugging
program download : JTAG emulator
UART 통신 : ISP programmer

24. Instruction Example :
int main(){ unsigned char *a,*b,*c; a = (unsigned char *)0x100; b = (unsigned char *)0x101; c = (unsigned char *)0x102; *c = *a + *b; return 0; }

25. Machine Code(Opcode) / Assembly Code
Compile/Download 후 Debug메뉴의 ‘Start Debugging’
View 메뉴의 ‘Disassembler’
F: LDS R25,0x0100
Load direct from data space
: LDS R24,0x0101
: 0F ADD R24,R25
Add without carry
: STS x0102,R24
Store direct to data space

26. Instruction Example :
int main(){ unsigned int *a,*b,*c; a = (unsigned int *)0x100; b = (unsigned int *)0x101; c = (unsigned int *)0x102; *c = *a + *b; return 0; }

27. Machine Code(Opcode) / Assembly Code
Program address
Opcode
Assembly Code

28. Instruction Example :
int main(){ unsigned int *a,*b,*c; a = (unsigned int *)0x100; b = (unsigned int *)0x102; c = (unsigned int *)0x104; return 0; }

29. Machine Code(Opcode) / Assembly Code
Program address
Opcode
Assembly Code

30. HEX File Compile 결과물의 하나 Project directory 아래 “default” 폴더
Intel Hex Format
: C C945D000C945D000C945D0013
: C945D000C945D000C945D000C945D00EC
: C945D000C945D000C945D000C945D00DC
: C945D000C945D000C945D000C945D00CC
: C945D000C945D000C945D000C945D00BC
: C945D000C945D000C945D000C945D00AC
: C945D000C945D000C945D000C945D009C
: C945D000C945D000C945D000C945D008C
: C945D000C945D000C945D FBE67 …

31. Intel Hex Format :100000000C9446000C945D000C945D000C945D0013 : 10 0000

32. Intel Hex Format 8-bit 16-bit address code 0x0000 0C 0x0001 94 0x000246
0x0003 00
0x0004
0x0005
0x0006 5D
0x0007
0x0008
0x0009
0x000A
0x000B
16-bit
Address
code
0x0000
940C
0x0001
0046
0x0002
0x0003
005D
0x0004
0x0005