Date : Sun, 16 Mar 2008 20:31:06 +0100 (GMT)
From : johan@... (Johan Heuseveldt)
Subject: TUBE chip, accessing 'Parasite' side
Hi Robert,
On Sun 09 Mar, Sprow wrote:
>
> In article <080309015504@...>,
> Jonathan Graham Harston <jgh@...> wrote:
>
> [contention logic]
>
> > Now that I think I know what you're talking about, though, I see
> > that the 6502 and Z80 copros feed PCS and HCS into an OR that
> > feeds the timing circuitry - probably your cycle stretching.
> > Interestingly, the 32016 and 80186 copros don't.
>
> More likely I would suggest that there's a possibility for a race condition
> if one processor is writing to one side just as the other processor is
> reading (polling) the same register other side.
I had come to similar conclusions, as previously posted. But no doubt I
used different words to describe! :-)
I quite like to see it confirmed by you! Thanks.
Starting with the idea of no problems with simultanous access from both
sides, I was quite confused to see the clock circuit tempered with in the
schematics of the 6502 2ndP, thinking of it as contention logic. Now I see
it may be regarded to prevent software racing issues.
So I continued my design the way I started. With the new facts known, I
decided not to include any of that. There is very little to gain here with
the 6809. Its interrupt design is much more of a problem, which I think I
have tackled!
I would like ask you foulks some other questions, and wonder if a new subject
is appropriate: further questions will have little to do with the access
issue discussed so far. My main concern is not poluting the thread, but also
not being rude to the archiving system.
Things on my mind are indeed my solutions for interrupts and choice of IC
family; old LS or newer HC/HCT.,This also in view of the GALs used.
Please let me know wether or not to start another thread; afresh or
replying with change of subject...
Greetings,
Johan
--
Johan Heuseveldt <johan@... >
aka waarland
The best place is a Riscy place
Are movies about Vulcans Pathe-logical?