CODEWITHSUNDEEP
assemblyz80
Kir
Kir

Reputation: 11

How can I get the range of numbers that would produce certain flag conditions when subtracted from 43h in Z80 assembly?

I started learning Z80 recently, but I'm struggling with flags.

I want to get the range of register "B" in Z80 assembly.

This is the problem that I faced. Register "A" is 43H (in Hexadecimal number) and I want to sub register "B" from that, doing in 8-bit subtraction.

How can I get the each range of register "B" that would produce:

Upvotes: 0

Views: 162

Answers (1)

prl
prl

Reputation: 12455

67 - x sets C if x > 67 or x < 0.
It sets S if x > 67 or x < -60.
It sets V if x < -60.

In unsigned hexadecimal, 43h - x sets C if x > 43h.
It sets S if x > 43h and x < c4h.
It sets V if x > 7fh and x < c4h.

Upvotes: 3

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