Re: ROMs replacement.. solved!

From: silverdr_at_wfmh.org.pl
Date: Fri, 19 Oct 2012 09:11:19 +0200
Message-Id: <4E8A6BAC-132B-4FCD-B53B-6445D1B80AD0@wfmh.org.pl>
On 19 paź 2012, at 08:02, Gerrit Heitsch <gerrit@laosinh.s.bawue.de> wrote:

>> Why? If I want to blend-in the content - say - as if it was loaded in RAM?
> 
> Yes, but you will need to tell the PLA about putting ROM where RAM would usually be.

Why? I put the ROM there, not PLA

> Otherwise the PLA will generate the _CAS signal for that address space and activate the RAM. That would mean RAM and ROM output drivers fighting it out and the system crashing.

No, I mean I grab the _CAS signals and select the ROM whenever address decodes properly. If not (or if my ROM is disabled), I pass it through. Not sure about the timing though.

> This 'telling the PLA about it' is done with the _EXROM and _GAME signals.

Yes, and keep it that way. Let the real cart push the lines so that in such case the real cart can still work and override my ROM.

Am I missing something?

-- 
SD!
       Message was sent through the cbm-hackers mailing list
Received on 2012-10-19 08:00:05

Archive generated by hypermail 2.2.0.