[A83] Re: microcode
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[A83] Re: microcode
From: Henk Poley <HPoley@DDS.nl>
>
>> Van: Sebastiaan Roodenburg <sebastiaan@rimsystems.nl>
>>
>> > Is it possible to make something in microcode?
>> > (these are the individual instructions which are
>> > executed with a z80 instruction)
>>
>> Nope... microcode is coded into a little piece of ROM inside the Z80, and
>> since ROM can't be changed... (maybe it can be done with a hardware
>> hack, but i doubt it)
>
>Yesterday I found a book my grandfather used when learning to program, it
Wow! Your grandfather! So there *are* actually 'old' people programming out
there
>handles the i8080 (horrible syntax), Z80 and M6800 (that's not the M68000
>>from the Ti89/92[+]).
It's its predecessor afaik
>Somewhere in the book I've found some things about
>microcode, so I'll take a look... Don't give you much of a chance it can be
>done, as far as I have read (Thomas Scherrer's hompage) the Z80 is one of
>the biggest CPU's which are "hardwired", which says as much as, "it doesn't
>use microcode".
>
>Could be that it does work with microcode, but then the problem arises that
>it wasn't that common to have reprogrammable ROM's, just because they were
>to expensive. I don't think that Ti has made an effort of getting a
>'reprogrammable' Z80... Most of the time Ti has chosen for the safer
>option, I don't thing that they want people to accidentally change their
>processor when trying 'secret' OP-codes, or crashing when their calc. And
>btw, what need would it have for Ti to be able to update the processor, one
>that has been used for about 20y by now?
Well, MMX, for example :)
> Henk Poley
>
>
>BTW: what was the mail you replied to? (did I miss something?)
>
>
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