Re: ROMs replacement.. solved!

From: Gerrit Heitsch <>
Date: Thu, 18 Oct 2012 19:00:12 +0200
Message-ID: <>
On 10/18/2012 12:22 AM, wrote:
> * - how about using the extra space for selecting-in some cart images? I mean I have a need for three KERNALs. Can imagine a need for four. Beyond that I find it difficult to imagine a daily use setup that would need more KERNALs always present. But I can imagine using  e. g. three or four KERNALs and one or two or three ROM cart images that would autoboot with CBM80 when selected at $8000. To make it best as I can think of now I would use the room for four KERNALs and two ROM carts.

That will need some extra wiring since you need to grab the _EXROM or 
_GAME line from the PLA and also their corresponding chip select lines.

The logic would then only decode the cart image if it also detects the 
matching _EXROM/_GAME line being low.

And you'll also need at least a 4 input AND gate (74LS21) for the 
_OE/_CS signal for the EPROM.

We're getting to the point where the logic is getting a bit out of hand. :)


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Received on 2012-10-18 18:00:11

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