Re: More CPLD explorations

From: Gerrit Heitsch <*gerrit_at_laosinh.s.bawue.de*> Date: Tue, 25 Feb 2014 19:21:52 +0100 Message-ID: <530CDF40.3020306@laosinh.s.bawue.de> · gerrit_at_laosinh.s.bawue.de

On 02/25/2014 07:07 PM, Bil Herd wrote:
> Yeah I remember the 3 seconds where I made the mistake on hiding the
> register in the VIC.  I thought to do a “lock the door and throw away
> the key” approach where only a cold start would bring it back in.

Judging from the schematics, the C128 has a signal (labeled '64/128') 
that seems to tell some of the logic what mode it is in. That could have 
gotten used together with an unused pin (which it has as far as I know) 
on the 48pin VIC to 'disappear' the registers in C64 mode.

That would also have prevented getting stuck with the registers gone in 
C128 mode.

> But then we never said it was 100% compatible. >:)

That's why I wrote 'almost'. It was still impressive.

> (we had a LOT of 7406/7s)

So I see... and most of them from Russia (EL74xx).

  Gerrit

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