Comment 11 for bug 584093

Hi, Debjit,

I couldnot comment on the patch you made because I donot know how to
recompile the simulater. If you could let me have the re-compiled version, I
will test it.

Regards, Felix Fung

2010/6/4 Debjit Biswas <email address hidden>

> Hi,
>
> I have created a patch for the DAA instruction. I observed that there
> were 3 basic errors in the DAA code which are as follows:
>
> 1. The most significant 4 bits (which is stored in the "high" variable) was
> being updated before the operation on the lower bits. It should be updated
> after the operation.
> 2. The overflow condition was being checked by comparing whether the
> operation on the 4 bits is producing a value greater than 9. This should
> compared with 15 (2^4 = 16).
> 3. The manual states that the Carry flag will be set if there is a overflow
> after the operation on the higher 4 bits, but it should not be unchanged if
> there is no overflow. The older code was resetting the flag if there was no
> overflow.
>
> I am attaching this patch. Can anyone please point to some sample code
> to test it with? I have tested a few examples I found in the manual, and
> the of course the code provided in the description of this bug :)
>
> -- Debjit
>
> ** Patch added: "daa.patch"
> http://launchpadlibrarian.net/49670414/daa.patch
>
> --
> 78+88 in BCD addition missed carry
> https://bugs.launchpad.net/bugs/584093
> You received this bug notification because you are a direct subscriber
> of the bug.
>
> Status in gnusim8085: Confirmed
>
> Bug description:
> With the following program, the carry flag is missed:
>
> mvi a,078h
> adi 088h
> daa
> hlt
>
> please check
>
> regards, Felix Fung
>
> To unsubscribe from this bug, go to:
> https://bugs.launchpad.net/gnusim8085/+bug/584093/+subscribe
>