16 Mar
2005
16 Mar
'05
2:59 a.m.
Hi,
Rumor has it that William Donzelli may have mentioned
these words:
>Parity checking is the job of the memory
controller, not the processor. In
>fact, I am having a hard time thinking of a processor that did its own
>parity checking in software (yes, I know any processor could do it, but
>did any really do it?).
8085? There's a P bit in the condition code
register (in 6809 speak) -- I
think it's called the PSW -- Program Status Word? I'm just beginning
learning assembly on my Tandy 10x/200 machines... Anyway, there are several
arithmetic operations that automatically set the Parity bit and there are
branch and return instructions that utilize the status of the P bit.
Yes, the 8080/8085/8086 series chips did parity checking. The PSW had a flag
for odd/even parity. Naturally, the Z80, being a superset of the 8080, also had this
ability. I assume that the later generations of x86 series chips, for backward
compatability,
also had the ability to check for parity.
The TMS9900 series also did parity checking.
From a cursory glance at the status registers of the
6809 and 68000 processors, it
appears these devices did not have inherent parity
checking.
river