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Accumulator has data FFH. Determine the state of CY, Z and sign flag when: 1) 01H is added 2) the content of the accumulator is incremented

Accumulator has data FFH. Determine the state of CY, Z and sign flag when: 1) 01H is added 2) the content of the accumulator is incremented Correct Answer <p>1) CY = 1, S = 0, Z = 1</p> <p>2) CY = same as previous state, S = 0, Z = 1</p>

Concept:

Sign Flag (S):

After any operation, if the MSB of the result is 1, it indicates the number is negative and the sign flag becomes set, i.e., 1.

If the MSB is 0, it indicates the number is positive and the sign flag becomes reset i.e., 0.

Zero Flag (Z):

After any arithmetical or logical operation if the result is 0 (00)H, the zero flags become set i.e., 1, otherwise it becomes reset i.e., 0.

Carry Flag (CY):

Carry is generated when performing n bit operations and the result is more than n bits,

Then this flag becomes set i.e., 1, otherwise, it becomes reset i.e., 0.

During subtraction (A - B), if A > B it becomes reset, and if (A < B) it becomes set.

Carry flag is also called borrow flag.

1-carry out from MSB bit on addition or borrow into MSB bit on subtraction.

0-no carry out or borrow into MSB bit.

Analysis:

1) When 01H is added

ADD A, #01H will increase the content of the Accumulator by 1. It will also change the content of carry (CY) flag.

[ alt="F31 Shubham B 12-5-2021 Swati D25" src="//storage.googleapis.com/tb-img/production/21/05/F31_Shubham%20B_12-5-2021_Swati_D25.png" style="width: 281px; height: 94px;">

The content of the flags are as follows:

Sign flag (S) = 0

Carry flag (CY) = 1

Zero flag (Z) = 1

2) When the content of the accumulator is incremented.

INR A will increase the content of the Accumulator by 1. Carry flag (CY) is unaffected by INR operation.

[ alt="F31 Shubham B 12-5-2021 Swati D26" src="//storage.googleapis.com/tb-img/production/21/05/F31_Shubham%20B_12-5-2021_Swati_D26.png" style="width: 281px; height: 94px;">

The content of the flags are as follows:

Sign flag (S) = 0

Carry flag (CY) = no change

Zero flag (Z) = 1

Hence from the above figure option (2) is correct

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