UGC NET CSE | December 2014 | Part 3 | Question: 06

Question

Specify the contents of the accumulator and the status of the $S, Z$ and $CY$ flags when $8085$ microprocessor performs addition of $87 H$ and $79 H$. 

• A. $11, 1, 1, 1$
• B. $10, 0, 1, 0$
• C. $01, 1, 0, 0$
• D. $00, 0, 1, 1$

Answer 1

Addition of 87H and 79H.

87 H  - 1 0 0 0 0 1 1 1

79 H -  0 1 1 1 1 0 0 1

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          1 0 0 0 0 0 0 0 0

S - sign flag - Since MSB of result is 0, hence sign bit should be 0.

Z - Zero flag - Since result is zero, hence zero bit should be 1.

CY - Carry flag - Since there is a carry from MSB (8th to 9th bit), hence CY = 1