Need help with questions 5 and 6 please Register ___ hold the quantity of times

Question

Need help with questions 5 and 6 please

Register ___ hold the quantity of times the loop is repeated. Explain how the DECB and BNE determine that the loop has completed the correct amount of repetitions. How is the beginning of the loop identified in the above program? The BNE instruction checks the ___ flag in the CCR and if the flag is set it ___ and if the flag is clear it ___. What would you change in the above program if you want it to loop 255 times? Add comments to the below program. COUNT EQU $1225; MYRAM EQU $1250; LDAA #15; STAA COUNT; CLRA; AGAIN ADDA #3; DEC COUNT; BNE AGAIN; STAA MYRAM;

Explanation / Answer

5) DEC B instruction decreases the value of B by 1.

BNE instruction checks the value of b in not equal to 0.

Suppose B=125,

DEC B ->125-1=124

BNE->1(24!=0)

Since 124 is !=0 it loops back to the label 'BACK'. This continues till the valu2 of b=0.At this point , the condition is not matched and it will come out of the loop and execute the next statement.

6)The DECB and BNE BACK instruction determines the begining of the loop.BNE check the value of b in not equal to 0 and if its true .it loops back to label 'BACK',Then DEC B decreases the value of B and the condition is checked again.Hence this determines that the loop has begun.

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