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

[Chad H]

The schematic notes I saw for the SLENB* online use the "*" to represent volts, or tying to ground.  I'm concerned however by the description: "Disable Internal Devices".  If it's just disabling the internal ROM's, fine, but we don't want to disable all kinds of other hardware in the process.

|     |             |                                      | 
| 36  |   SCS*      | Spare Cartridge (DISK) Select Signal | 
| 37  |   ADDR 13   | CPU Address Bus - Bit 13             | 
| 38  |   ADDR 14   | CPU Address Bus - Bit 14             | 
| 39  |   ADDR 15   | CPU Address Bus - Bit 15             | 
| 40  |   SLENB*    | Input to Disable Internal Devices    | 
------------------------------------------------------------ 
* are LOW (0 volts) to activate

-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Camillus Blockx
Sent: Saturday, December 13, 2014 2:48 PM
To: Bill Pierce via Coco
Subject: Re: [Coco] FW: CoCO EPROM -- 32K test??

To give you an answer on SLENB* I have to see some schematics, I can see that the star (*) denotes something but is that mean negative active or what??  So if you have any schematic of you board I would glad to help to build a smal tester.

cb

On 12/13/2014 2:41:52 PM, Chad H <chadbh74 at hotmail.com> wrote:
That's interesting. Well the cartridge should already be 'decoding' up to 32K. If it is, the only thing missing would be the SLENB*. What is happening there? Tying it to +5V or GND? If that's the only thing missing, it seems plausible someone could make this small mod (jumper?) and use the cartridge to 'Upgrade' their CB to ECB, or to a modded version of it.

-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Darren A
Sent: Saturday, December 13, 2014 1:40 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] FW: CoCO EPROM -- 32K test??

On Sat, Dec 13, 2014 at 11:54 AM, Chad H 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.



The CoCo 1 and 2 can access 32K cartridge ROM, but it would require the addition of an address decoding circuit on the cartridge. You would need to decode the additional 16K (8000-BFFF) and assert the SLENB* cartridge pin to override the internal ROM selection.

Darren

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