Re: Eagle CAD design and fabrication of C64 & Plus4 cartridges

From: Jim Brain <>
Date: Sat, 3 Jun 2017 18:48:18 -0500
Message-ID: <>
On 6/3/2017 11:15 AM, bwack wrote:
> Hi Jim and Mark. I became one of the testers. I accepted to receive and make
> a video about it. I didn't know about this discussion at the time, and that
> it was a quick mash-up, so this turned more into a pcb 1.0 review than an
> easy of use review.
> I've learned that the cartridge sets #EXROM or #GAME, and in some cases both
> (16k). Then, why is there a double throw jumper for #EXROM and #GAME?
I believe you're trying to use the single ROM cart design for a 16kB 
cart.  I don't think that will work, or at least I never designed it to 
do so.  The design parms for the single EPROM cart was to support 
putting an 8kB ROM at either ROML or ROMHI had
> One chipselect/outputenable, two chipselect signals:
> Now the second thing I gather is that the PLA drives #CS and or #OE with
> #ROML or #ROMH. Those signals are dependent on #EXROM and #GAME. Because the
> overview doc I got from Mindflare says : "Single EPROM support - 2764 or
> 27C64 (1 x 8k bank) / 27128 or 27C128 (2 x 8k banks)", I decided to buy an
> 27C128. Here is the problem: a double throw jumper has no place on selecting
> #ROML and #ROMH for #OE. It's either #ROML or both, right? The second
> problem: I have a single chip, but two chipselect/output enable drivers
> #ROMH and #ROML. Someone in the thread suggested two diodes and a resistor.
> This was not everything needed to make it work. The #ROML was also connected
> to A13, the MSB of 27c128's address bus.
I don't know.  as far as I can tell from the schematic, that cannot happen.


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Received on 2017-06-04 00:00:02

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