[Coco] FW: CoCO EPROM -- 32K test??

[Camillus Blockx]

Hi chad, I think you can do a simple test.

An erased eprom will have all  &HFF at his data bus when empty, right.
Now if you program an eprom ( pin compatible eeprom is ok too, saves you the UV erase time ) on some specific addresses in the address space of the eprom, I presume this is a 15 bit address space, let say 9 ( 3 in low address, 3 in mid address, 3 in high address ), with a pattern of 01011010 = &H5  Make note of the addresses you picked.

address:   A15---------------------A0    A15---------------------A0    A15---------------------A0
e.g.             00011 00000 00000         00000 00011 00000       00000 00000 00011

Now put this rom into your device, select the 32K  range, add some power to he board and make the address pins rom the eprom high by connecting them to the + 5V ( this means you have to connect 2 address pins per test  ).

Now you just have to see if the voltage on the data bus is in line with the pattern you programmed.

This test is faster done then explained...LOL
Hope you could follow and sorry for my english it is not my native language, writing that is even worse...LOL

Anyway hope this helps. My coco is on the bench in ICU otherwise I would love to test it for you.
camillus
On 12/13/2014 12:55:24 PM, Chad H <chadbh74 at hotmail.com> wrote:
Well that sucks. But I guess if the CoCo 2 could be made to access 32k blocks of cartridge ROM someone would have already done it. I could acquire a CoCo 3 but a quick look on EBay shows they are not so cheap. What would be nice is if I had a 'tester' I could plug the cartridge and that device be designed just for performing memory/diagnostic checks on the cartridge.. Who knows, maybe I will build one some day. I guess in the mean time I will put out these revised boards with the 32k option as "experimental" until I receive feedback confirming that it works. I remain confident that it will as I employed the same method and logic used on the A13 line for 8k/16k banking to the A14 line. Its curious to me that Tandy had all 16 address lines going into the cartridge interface so could have addressed 64k ROMs but never gave the CoCo the memory management hardware to do so....ugh. Maybe whoever eventually comes up with a "CoCo 4" with cartridge support will do so.

These boards are my latest revision of Mark Blair’s original CoCo EPROM Pak. I continue to give him full due credit for without his design I would have had to start from scratch. This is still his board as far as I’m concerned….just revised.



If anyone is interested, I have built the first board and tested it (8K/16K banking only since I have a CoCo 2.) and listed it on E-Bay here along with further documentation and photos.



http://tinyurl.com/ood6a5k



Thanks!



-------- Original Message --------
From: Chad H
Sent: Friday, December 12, 2014 11:36 PM
To: 'CoCoList for Color Computer Enthusiasts'
Subject: RE: [Coco] CoCO EPROM -- 32K test??

Ummm....What???????

The "16k" select it could always do, I am not desiring to test that. I'm wanting to read/verify/test a full 32K of EPROM code, that's what the latest revision adds. There are already jumpers to select up to 4 x 16K segments or 8 x 8K segments. This newest revision offers up to 2 x 32K segments..need to test it.

-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Robert Gault
Sent: Friday, December 12, 2014 9:28 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] CoCO EPROM -- 32K test??

Chad H wrote:
> OK, so I finally got around to ordering the first batch of the modded
> EPROM boards that will do 32K banking in addition to the 8K or 16K
> banking it was already capable of doing. I went into this knowing it
> would probably only be useful to those with CoCo 3's, which I am not one.
>
>
>
> At this point, however, I really would like to test it to make sure
> it's fully operational as expected. I do have 27256/27512 EPROM
> available but only a CoCo 2 to test it in. Is there a way I could go
> about this with what I have?
>
>
>
> - Chad
>
>

You will need to add some switches that can permit you to select the desired 16k bank of the EPROM. That is reasonably simple to wire.

Robert


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