Re: MAX Machine PLA

From: Segher Boessenkool <>
Date: Fri, 29 Jul 2016 22:59:58 -0500
Message-ID: <>
On Fri, Jul 29, 2016 at 10:51:20PM -0400, Pete Rittwage wrote:
> > However, it is not the Signetics PLA used on other Commodore products.
> > It has 11 inputs and 15 outpus, and I cannot find any information about
> > it on the Web. But before I start reverse-engineering it on my own, I'd
> > like to ask here if there is any info avilable on this chip?
> I'm quite surprised the MAX has a PLA. I didn't think it had any
> alternative memory configurations, so it is likely a very simplified
> version of the C64 version handling only the RAM timings, etc.

It decodes the top 6 address lines and the BA signal (from VIC, it says
if VIC resp. the CPU is doing a memory access) to the various chip select
signals (ROML ROMH VIC SID COLRAM CIA RAM EXRAM), forces all VIC accesses
to reads, and connects D0..D3 to D8..D1 for CPU accesses to the colour RAM.

It may be similar internally to the PLA "clone" Commodore made.  Or it
may not be :-)


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Received on 2016-07-30 04:00:41

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