[Coco] eprom programmer

[Frank Pittel]

I'm thinking the same thing!! :-) I just need to figure out which ROM version
I would want besides drivewire. I do have a scsi adaptor but to use that with
a floppy controller means I'd need an MPI and I've got a SuperIDE with the a
version of jdb-dos with scsi support. It's nice to have the option though!

The Other Frank


On Sat, Mar 24, 2012 at 01:32:49PM -0500, Chad H wrote:
> Hmm...Sounds like a project..Maybe I could select between DECB & HDBDOS
> (DriveWire) that way.
> 
> -----Original Message-----
> From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com] On
> Behalf Of Darren A
> Sent: Saturday, March 24, 2012 12:40 PM
> To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] eprom programmer
> 
> On Sat, Mar 24, 2012 at 10:49 AM, Chad H wrote:
> > Hmm...so let me see if my thinking is correct here...
> >
> > I currently have a 8K 2764 EPROM in my 502 Controller... If I replaced 
> > this with a 27128 16K chip I could combine 2 .ROM files, write them, 
> > but I would be stuck on either the low or high bank.
> >
> > Now Darren said the high address line was tied to Vcc on the controller.
> > What if I removed that and ran the Vcc to a switch along with ground 
> > and used the switch to flip Vcc/Ground on the high address pin...  
> > Would this achieve the bank switching effect?
> >
> 
> Yes.  You would need to bend out pin 26 (A13) on the EPROM or perhaps cut
> the trace on the board.  Then connect a switch to that pin which toggles
> between Vcc/Gnd and you have a switchable, banked EPROM.
> 
> A more elaborate modification would be to do the same with pins 1 and 27,
> then you can use a 27512 EPROM with eight banks of 8K.
> 
> Or..connect pin 26 to the CPU address line A13 and only put switches on pins
> 1 and 27, giving you four banks of 16K.
> 
> Darren
> 
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