[Coco] Need a FD 502 controller that can accept 28 pin roms

[Little John]

Okay - I thought that was what Darren A was saying but wasn't sure.
----- Original Message ----- 
From: "Arthur Flexser" <flexser at fiu.edu>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Wednesday, October 13, 2010 1:15 AM
Subject: Re: [Coco] Need a FD 502 controller that can accept 28 pin roms



> That modification is only necessary because Extended ADOS-3 requires 16K 

> of

> EPROM space;  for an 8K DOS, the FD502 works fine as is, even if the DOS 

> is

> in a 27128 or 27512, so long as the code is in the correct 8K of the chip.

> The relevant address line is grounded on the FD502, and the modification

> requires cutting a trace to un-ground it along with running a jumper wire 

> to

> the edge connector.

>

> Art

> On Wed, Oct 13, 2010 at 2:03 AM, Little John <sales at gimechip.com> wrote:

>

>> Cool. I was going by what I had read in the Extended ADOS-3 Manual which

>> states:

>> If you have the Tandy FD-502 controller, you already have a 28-pin 

>> socket:

>> however, the controller needs a minor modification in order to be usable

>> with a 27128 EPROM.

>> It then mentions how to get the instructions from SpectroSystems, 

>> followed

>> by:

>> The instructions may also be found on Page 76 of the March 1989 Rainbow

>> magazine except that there is a typographical error: It is pin 26 not pin 

>> 28

>> that must be connected to the controller's edge connector.

>>

>> But are you saying it can handle a 16K EPROM without modifications? or 

>> are

>> you saying that it can use any 2764-27512, but only as an 8K device? Just

>> curious. I use 27256's for everything because I have a ton of them - I 

>> just

>> burn an 8K image into the 27256 stacked 4 times - so it doesn't matter 

>> the

>> status of the upper address lines or even if they are floating - it still

>> works.

>>

>> If HDB-DOS is only 8K then it would be fine without mods, but if you 

>> tried

>> a 16K DOS (like CoCoNet) it would need the mod - I think?

>> -John #1

>>

>>

>> ----- Original Message ----- From: "Darren A" <mechacoco at gmail.com>

>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>

>> Sent: Wednesday, October 13, 2010 12:24 AM

>> Subject: Re: [Coco] Need a FD 502 controller that can accept 28 pin roms

>>

>>

>> On 10/12/10, Little John wrote:

>>>

>>>> The FD-501 drives will work with the FD-502 controller (or pretty much

>>>> any

>>>> coco controller). I may be mistaken, but I believe that the FD-502,

>>>> although

>>>> having a 28-pin socket, is still only wired for an 8K eprom and the

>>>> additional address line will still need to be hacked into the socket 

>>>> with

>>>> a

>>>> jumper wire. Can anyone else confirm this?

>>>>

>>>

>>> The FD-502 will accept anything from a 2764 to 27512 without

>>> modification.  For anything larger than a 2764, the code must be

>>> programmed into the upper-most 8K of the device.

>>>

>>> Darren

>>>

>>> --

>>> Coco mailing list

>>> Coco at maltedmedia.com

>>> http://five.pairlist.net/mailman/listinfo/coco

>>>

>>

>>

>> --

>> Coco mailing list

>> Coco at maltedmedia.com

>> http://five.pairlist.net/mailman/listinfo/coco

>>

>

> --

> Coco mailing list

> Coco at maltedmedia.com

> http://five.pairlist.net/mailman/listinfo/coco