Re: More CPLD explorations

From: Nate Lawson <>
Date: Mon, 24 Feb 2014 20:57:58 -0800
Message-Id: <>
On Feb 24, 2014, at 7:51 PM, Jim Brain <> wrote:

> This time, it's PLA replacements.
> After fitting, the C64 PLA equations take only a nominal portion of the xc9536(xl) space I stuffed them into.  And, none of the 36 registers are used.
> I know SuperPLA put a bunch of equations in the unit, for different products, but I was wondering...
> Are there any memory mappings that would have been nice to have via the PLA, but are not available?  (external KERNAL at $e000, for instance?)
> Yes, I understand compatibility and all that.  But, if you had a switchable PLA, what new modes would be of interest? (are there any?)

A couple (jim)brainstorms:

1. If there are multiple versions of the PLA, logic to switch to a given version, based on user writes to reserved combinations of address 0/1.

2. Add a very small VIC coprocessor where 6502 instructions are packed into your CPLD registers and scan line is detected via the VIC address patterns. You know, an Amiga-like copper in a C64.

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Received on 2014-02-25 05:01:36

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