Answer to Question #262471 in Assembler for talltim

Question

Assume that you have a machine, as shown in section 3.2.2 of Block 3 having the microoperations given in Figure 10 on page 62 of Block 3. Consider that R1 and R2 both are 8-bit registers and contain 11110000 and 00110110 respectively. What will be the values of select inputs, carry-in input, and result of the operation (including carry out bit) if the following microoperations are performed? (For each micro-operation you may assume the initial value of R1

and R2 as given above)

(i) Decrement R1

(ii) Add R1 and R2 with carry

(iii)AND R1 and R2

(iv) Shift right R1

Answer 1

(i) Decrement R1

R1=1111 0000

DEC R1           ; R1 =1110 1111

 

(ii) Add R1 and R2 with carry

R1=1111 0000

R2=0011 0110

R1 ADD R2 :     0010 0110

Carry: 1

 

(iii)AND R1 and R2

R1=1111 0000

R2=0011 0110

R1 AND R2 :     0011 0000

 

(iv) Shift right R1

R1=1111 0000

R1 Shift right on one ; R1=1111 1000