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Lightweight 8051 compatible CPU

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AC bit result wrong in SUBB #4
Open cycasabc opened this issue about 8 years ago
cycasabc commented about 8 years ago

The AC bit after executed SUBB instruction seems to be wrong. For example, executing "SUBB A, R0", if A=0x0a, R0=0x10, AC bit should be clear, but current result is set.

I go through the source code, in line 227 of light52_alu.vhdl, it seems condition "1101" should not be used for AC bit set, is it right?

Thanks & Regards

ja_rd commented over 6 years ago

After porting this project to Github at https://github.com/jaruiz/light52, I thought this bug ticket had been ported too, and fixed.

But I can see it isn't. The bug is still there as far as I can tell.

So I have reopen it in Github:

https://github.com/jaruiz/light52/issues/1

I am ashamed to have procrastinated so much on this bug. I should at least have posted a comment here for the benefit of the submitter. My apologies!

Please track this bug on GitHub. It'll be closed here as soon as it is closed there.

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