[Coco] Need a FD 502 controller that can accept 28 pin roms
sales at gimechip.com
Wed Oct 13 12:15:30 EDT 2010
the CoCo 3 could have accessed almost the entire 32K of ROM - it would have
allowed some cool stuff.
----- Original Message -----
From: "Arthur Flexser" <flexser at fiu.edu>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, October 13, 2010 1:45 AM
Subject: Re: [Coco] Need a FD 502 controller that can accept 28 pin roms
> Ah! I had misremembered that the pin was grounded rather than tied high
> the FD502, and was therefore puzzled as to why the code had to be in the
> UPPERmost 8K. Thanks for the correction!
> This brings to mind an exchange I had at a Rainbowfest with Tandy's Mark
> Siegel, who was the main guy involved with CoCo development (and the
> speaker at that fest). I mentioned how easy it would have been to enable
> the full address space on the FD502 rather than tying that line high or
> and expressed the wish that any subsequent CoCo controllers have that
> feature. He agreed suspiciously quickly to implement this change on
> CoCo controllers.
> On Wed, Oct 13, 2010 at 2:29 AM, Darren A <mechacoco at gmail.com> wrote:
>> On 10/13/10, Little John <sales at gimechip.com> wrote:
>> > Okay - I thought that was what Darren A was saying but wasn't sure.
>> Yes. The FD-502 ROM socket is only wired for 8K (A0-A12). You need to
>> run a jumper wire for A13 if you want to use a 16K EPROM.
>> The other pins which become address lines on larger EPROMS are all
>> tied to Vcc, thus the need to put the code in the upper-most 8K of the
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