about intel 8085

[dushyanthofpes]

i had programmed the 8085 to take in (11111111)binary that is
ff(hexadecimal) into the accumalator and complemented it and observed that the zero flag was'nt affected.can anybody give a logical reasoning to this observation

[SwedaGuy]

According to the Intel 8080/8085 Microprocessor book, no flags should be affected.

If my memory serves me correctly, issuing an immediate logical OR with 00h (ORI 00h) should set the Z flag without affecting the contents of A. If someone else thinks I'm wrong about this, please correct me.

Actually, now that I think about it, just OR A with A (ORA A), it's a single byte/single cycle instruction that way...

[ahm]

I'm certain either (a) it's supposed to do that, or (b) you did something wrong.
Without something more specific to work with, that's probably the best answer you're going to get.

[Thrashbarg]

http://thesatya.com/8085crd.txt

In the third column of the Op-Codes list (SZAPC) you will find what flags are changed by what Op-Codes. In this case you're interested in the Z column.

You will find that MOV, MVI, LDA etc and CMA don't change any flags.