Question

Provide Atmel AVR assembly language statements to implement the following
pseudocodes. You can assume that all the variables A, B, C, D correspond to CPU general purpose
registers as follows: A →R0, B→R1, C→R2, D→R3. You can also use additional registers from R4-
R31 as needed. You must not use any variant of the multiplication instructions. Your assembly code
segments should be properly commented.

(a) if D < 0
C = A+B
else
C = A-B
(b) if D < 3

C = A+B
elseif D < 5
C = A - B
else
C = A + 8*B

Answer 1

a.)

MOV R3,D    //moves the value from D to R3

MOV R0,A    //moves the value from A to R0

MOV R1,B    //moves the value from B to R1

MOV R2,C    //moves the value from C to R2

CMP R3,00   //compares R3 with 0

JMP less    // if less then go to "less" section

SUB R0,R1   //else R0=R0-R1

MOV R2,R0   //move the value from R0 to R2

less: ADD R0,R1        //add R0=R0+R1

        MOV R2,R0      //move the value from R0 to R2

b.)

MOV R3,D      //moves the value from D to R3

MOV R0,A      //moves the value from A to R0

MOV R1,B      //moves the value from B to R1

MOV R2,C      //moves the value from C to R2

CMP R3,3     // compare R3 with 3

JMP less3    //jump to "less3" if R3<3
 
CMP R3,5     //compare R3 with 5

JMP less5    //jump to "less3" if R3<5

MOV AX,8     //else move 8 into accumulator to perform multiplication

MUL R1       //multiply R1 with accumulator AX=AX*R1

MOV R1,AX    //move the value from AX to R1

ADD R0,R1     //add R0and R1 and store thr result in R0

MOV R2,R0     //finally move the value from R0 to R2

less3: ADD R0,R1

       MOV R2,R0

less5: SUB R0,R1

       MOV R2,R0