ATmega128 Assembly Language Programming

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1 마이크로프로세서응용 7 ATmega128 Assembly Language Programming

2 Assembly Language g Field Delimiter Field structure a space or colon after a label a space after the operation code a comma between operands in the address field +/- sign indicate post-increment/pre-decrement addressing a space after an instruction, semi-colon before an entire line means comments

3 Labels Label Field Only first eight characters of a label is meaningful First character must be an upper-case letter or dot character Meaningful word is helfpul for understanding

4 Assembler Directives Assembler Directives.CSEG,.DSEG : Code Segment, Data Segment.ORG : set location counter to origin to specify the starting address of main program to specify the starting address of subroutines to define areas of memory for data storage to define areas of memory for user stacks.org 0x0000,.ORG 0x0100.EQU : define a permanent symbolic name.equ LF = $0A.DB : define constant byte data.db $01, $02, $03, $04.BYTE: define byte storage.byte 4

5 Beginning g program 1-1 : Simple Move 8 bit DATA transfer : Input : value () = $73 Output: result () = $73 value result $73 value result $73 $73

6 Beginning g program 1-1.include "m128def.inc.cseg.org 0x0000 ; JMP RESET ;.ORG 0x0046; ; Main Program value result $73 RESET: ldi r16, $73 ; sts, r16 ; forever: value: result: lds r0, ; sts, r0 ; rjmp forever ;.DSEG.db 1.db 1 value result $73 $73

7 Beginning g program 1-2 : Simple Move 8 bit DATA transfer using Register Indirect Addressing : Input : value () = $74 Output: result () = $74 $74 $74 $74

8 Beginning g program 1-2.include "m128def.inc.cseg.org 0x0000 ; JMP RESET $74 RESET:.ORG 0x0046; ldi XH, HIGH() ; ldi XL, LOW() ; forever:.dseg value:.db 2 ldi r16, $74 ; st X, r16 ; ld r0, X+ ; st X, r0 ; rjmp forever ; $74 $74

9 Beginning g program 2-1 : Complement Form the bitwise complement of contents of 8 bit value VALUE at location Input : VALUE () = $74 Output: RESULT ($1010) = $8B $74 $8B

10 Beginning g program 2-1 : Complement.include "m128def.inc.cseg.org 0x0000 ; JMP RESET ; $74 RESET:.ORG 0x0046; ldi ldi XH, HIGH(); XL, LOW(); Set X register to the address of Fill the data $74 at the memory ldi r16, $74; st X, r16 ; ld r0, X+; com r0; st X, r0; Get the data from the memory, complement, and store it to the same location $8B forever: rjmp forever ;.DSEG.db 2

11 Beginning g program 2-2 : Simple ADD Add the contents of 8bit data at to the contents of 8bit data at and place the results in 8bit result at $0102. Input : VALUE1 () = $12 VALUE2 () = $34 Output: RESULT ($0102) = $46 $0102 $12 $34 $12 $34 $0102 $46

12 Beginning g program 2-2 : Simple Add.include "m128def.inc.cseg RESET:.ORG 0x0000 ; JMP RESET ;.ORG 0x0046; ldi YH, HIGH() ; ldi YL, LOW() ; ldi r16, $12; st Y, r16 ; ldi r16, $34 ; std Y+1, r16 ; $0102 $12 $34 forever: ld r0, Y+ ; ld r1, Y+ ; add r0, r1 ; st Y, r0 ; rjmp forever ; $0102 $12 $34 $46.DSEG.db 3

13 Beginning g program 2-3: Logical Shift Shift the contents of 8bit variable VALUE at to the left one bit. Store the result back in value Input : VALUE () = $75 Output: VALUE () = $EA $75 $EA

14 Beginning g program 2-3 : Logical Shift.include "m128def.inc.cseg.org 0x0000 ; JMP RESET ; $75 RESET:.ORG 0x0046; ldi ZH, HIGH() ; ldi ZL, LOW() ; ldi r16, $75; st Z, r16 ; ld r0, Z; lsl r0; st Z, r0; $EA forever: rjmp.dseg.db 2 forever;

15 Beginning g program 2-4 : AND Operation Divide the 8bit data in VALUE at into two 4bit data and store them as : Input : VALUE () = 5F Output: RESULT () = 05 ($0102) = 0F $0102 $5F $5F $0102

16 Beginning g program 2-4 : AND Operation.include "m128def.inc.cseg.org 0x0000 ; JMP RESET ; RESET:.ORG 0x0046; ldi ldi ZH, HIGH(); ZL, LOW(); Set X register to the address of Fill the data $5F at the memory $0102 $5F ldi r16, $5F; st Z, r16 ; ld r16, Z; lsr r16 ; lsr r16 ; lsr r16 ; lsr r16 ; std Z+1, r16; ld r16, Z; andi r16, $0F; std Z+2, r16; Get the data from the memory, logical shift right 4 times, and store it at the first result position. $0102 $5F Get the data again, and mask the data with $0F, the second nibble is stored at the second result. forever: rjmp forever;

17 Beginning g program 2-5: Compare & Br Find the larger of two 8bit variables VALUE1() and VALUE2(). Place the result in variable RESULT($0102). Assume the values are unsigned. Input : VALUE1 () = $76 VALUE2 () = $35 Output: RESULT ($0102) = $76 $0102 $76 $35 $76 $35 $0102 $76

18 Beginning g program 2-5: Compare & Br.include "m128def.inc.cseg.org 0x0000 ; JMP RESET ; RESET: BigR1: BigR0: forever:.org 0x0046; ldi ZH, HIGH() ; ldi ZL, LOW() ; ldi r16, $76; st Z, r16 ; ldi r16, $35; std Z+1, r16; ld ld r0, Z+; r1, Z+; cp r0, r1; brge BigR0; st Z, r1 ; jmp forever ; st Z, r0 ; rjmp forever ; Set Z register to the address of Fill the data $76 and $35 at the $01 00 and $1001 mem ory, respectively. Move the data from the memory to r0 & r1, compare two data, and branch to BigR0 if r0 >= r1 This routine performs only when r0 < r1. Then stores r1 to $0102 memory and jump to forever This routine performs only when r0 >= r1. Store r0 to $0102. $0102 $0102 $76 $35 $76 $35 $76

19 Simple Program Loops Program Loop Forces the CPU to repeat a sequence of instructions Loop component Initialization Section (counters, pointers, & other variables) Processing Section ( actual data manipulation ) Loop control Section (updates counters, pointers for next iteration) Concluding Section ( analyze and store the results )

20 Flow charts for program loop (Type A) start no Initialization section Processing section Loop control section Complete? yes Concluding section Start : int I, sum ; sum = 0 ; ptr = &data[0] ; counter = N ; Here : sum = sum + *ptr++ ; counter = counter 1 ; if counter > 0 goto Here ; result = sum ; end : end

21 Flow charts for program loop (Type B) Start : Processing section no start Initialization section Loop control section Complete? yes Concluding section it int I, sum ; sum = 0 ; ptr = &data[0] ; counter = N ; Here: counter = counter 1 ; if counter < goto o There e ; sum = sum + *ptr++ ; goto Here ; There: end End : result = sum ;

22 Flow Control 3-1 : Simple Loop Calculate the sum of 1 ~ 10 Output : Result () = $37 #include <stdio.h> main() { char i, sum ; (char = 8bit integer) sum = 0 ; for ( i = 1 ; i < 11 ; i++) sum += i ; // print the result to I/O $37

23 Flow Control 3-1 : Simple Loop.include "m128def.inc.cseg.org 0x0000 ; JMP RESET ; RESET:.ORG 0x0046; ldi ZH, HIGH() ; ldi ZL, LOW() ; ldi r16, 0 ; r16 = sum ldi r17, 1 ; r17 = i LoopStart: cpi r17, 11 ; brsh LoopEnd ; LoopEnd: add r16, r17 ; subi r17, -1 ; rjmp LoopStart ; st Z, r16 ; Set Z register to the address of Initialization: sum = 0 ; i = 0; LoopControl : if ( i < 11 ) goto loopexit LoopBody : sum += i ; i ++ ; Conclude Section: Store the result $37 forever: rjmp forever;

24 Flow Control 3-2 : 16Bit Operation in Loop Calculate the sum of 1 ~ 100 : (5050 = $13BA) Output : Result () = $BA = $13 #include <stdio.h> main() { int i, sum ; //(int = 16 bit) sum = 0 ; for ( i = 1 ; i < 101 ; i++) sum += i ; // print the result to I/O $BA $13

25 Flow Control 3-2 : 16Bit Operation in Loop.include "m128def.inc ;----- Register definition.def i_lo = r16.def i_hi = r17.def Sum_LO = r18.def Sum_HI = r19.cseg RESET:.ORG 0x0000 ; JMP RESET ;.ORG 0x0046; ldi ZH, HIGH(); ldi ZL, LOW(); LoopEnd: forever: add Sum_LO, i_lo; adc Sum_HI, i_hi; subi i_ LO, LOW(-1); sbci i_hi, HIGH(-1); rjmp LoopStart; st Z+, Sum_LO; st Z, Sum_HI; rjmp forever; ldi Sum_HI, 0; ldi Sum_LO, 0; ldi i_hi, HIGH(1); ldi i_lo, LOW(1); LoopStart: cpi i_lo, LOW(101); ldi r30, HIGH(101); cpc i_hi, r30; brge LoopEnd; $BA $13

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AVR ISA & AVR Programming (I) Lecturer: Sri Parameswaran Notes by: Annie Guo

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