RE: 8501 datasheet / information is wanted :)

The 8501 probably could be made to act like a 6502 by tying the gate line in
the right polarity.  My advice would be get some regular 6502's due to
better and more standard documentation plus the SYNC line is available for
better debugging if you ever want to clamp a debugger on it.

The 6532 was our main goto chip in the old days thought I have to admit I
fell in love with some of NEC versions with built in peripherals.

Bil

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Hegedus István
Sent: Monday, February 04, 2013 3:55 PM
To: cbm-hackers@musoftware.de
Subject: Re: 8501 datasheet / information is wanted :)

Once Bil Herd has already mentioned how the GATE IN signal works. It is just
a transparent latch which is responsible for R/W hold off during write
cycles. He said in the early 264 series prototypes he has used a 6502 CPU
with external transparent latch as GATE IN.
Despite this, I still have to understand the exact behavior :-)

Istvan

-----Original Message-----
From: Gerrit Heitsch
Sent: Monday, February 04, 2013 4:45 PM
To: cbm-hackers@musoftware.de
Subject: Re: 8501 datasheet / information is wanted :)

On 02/03/2013 10:48 PM, Gábor Lénárt wrote:
> On Sun, Feb 03, 2013 at 07:50:22PM +0100, Gerrit Heitsch wrote:
>>> The test circuit has UM6502 currently, so some modification is
>>> needed, I guess (I even don't know if 8501 needs two phase clock or
>>> not, etc).
>>
>> The 8501 needs only PHI0. But, in order for R/_W to  work properly,
>> you also need to supply a clock signal to the GATE IN pin. In the
>> C16, they use the MUX-signal for that.
>
> Ouch, that's new for me, I mean "gate in". Is there any information
> how can I use that?

I still haven't completly figured out how that signal works, but it has
something to do with the R/_W signal and the variable clock frequency of the
8501.




> Probably better to
> stay with UM6502 for me, it seems ... There are tons of tips for that
> for creating a minimal 6502 based system, and not so much worth just
> for an on-CPU I/O port, which was the reason I've started to think on
> this.

Again, the ideal chip for a minimal 6502 system is a 6532 since it will
supply you with lots of I/O, timer and 128 Bytes of RAM. That means all you
need is the 6502, a 6532, an EPROM and possibly one or two 74LSxxx.

  Gerrit





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