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

[Camillus Blockx]

The way I read is that when SLENB* is pulled to ground no rom is selected inside the coco. If this means that ALL roms are disabled then I don't see much working from the cartridge rom besides code that is completely on is own, and will never acces the BASIC ROM(s) ( would be impossible for coco2 ). 


Coco 3 on the other hand, moves everything from rom to ram and here it does not matter if the ROMs are disabled. I think that is what Tandy does anyway after copying the roms to ram. 

All depends now what SLENB* exactly does, and I will take the manual and schematics from the coco3 at hand and look at it, for better understanding. I follow this closely.

cb
On 12/13/2014 4:14:18 PM, William Astle <lost at l-w.ca> wrote:
You need to assert SLENB* *only* when the requested address is one you
are handling. That is, if your address decode decides to activate the
ROM or whatever on your cartridge. You can't just assert it
unconditionally without causing other trouble.

On 14-12-13 02:59 PM, Chad H wrote:
> 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 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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