I am not able to locate where the "ROMR" signal that goes in the 2K BIOS ROM is originated (datasheet, Circuit 1.pdf).
Any clue ?
where the /ROMR signal is originated?
Re: where the /ROMR signal is originated?
Hi,
/ROMR (or ROMreturn as i like to call it) is thru an inserted cartridge normaly connected to /ROM0 (the chipselect signal for the uppermost 16k (BIOS region))
in the CSL cartridge and the MegaSDCart we use /ROM0 to use an external BIOS
the parallel interface takes /ROM0 uses a part of it and returns the rest to /ROMR
Cheers, TOM:0)
/ROMR (or ROMreturn as i like to call it) is thru an inserted cartridge normaly connected to /ROM0 (the chipselect signal for the uppermost 16k (BIOS region))
in the CSL cartridge and the MegaSDCart we use /ROM0 to use an external BIOS
the parallel interface takes /ROM0 uses a part of it and returns the rest to /ROMR
Cheers, TOM:0)
http://www.8bit-homecomputermuseum.at Find me here...
Re: where the /ROMR signal is originated?
ok thanks, so if I've understood correctly /ROMR is used by an external cartridge when it wants to use the BIOS ROM; it does that by sending back the /ROM0 signal. If instead the cart wants to use its own ROM then /ROMR is just kept high for all the time.
This also implies that when you turn on a CreatiVision without a cart, it just executes random code because the BIOS ROM is never selected, right?
Apart from CSL and MegaSDCart, are there any cartridges that do not use the BIOS ROM ? I guess not.
This also implies that when you turn on a CreatiVision without a cart, it just executes random code because the BIOS ROM is never selected, right?
Apart from CSL and MegaSDCart, are there any cartridges that do not use the BIOS ROM ? I guess not.
Re: where the /ROMR signal is originated?
Hi,
Yes, you are correct :0)
1) All gamecartridges use the internal BIOS (/ROM0 is simply connected to /ROMR on the game PCB)
2) CSL and MegaSDCart use /ROM0 for themself (to replace the internal BIOS) and give nothing back to /ROMR (or pull /ROMR high)
3) the parallel Interface divides the 16k /ROM0 romselect into 8x 2k ROM areas - uses $E800-$F000 for itself - combines the remaining 7x 2k into 1 signal and gives this signal back as /ROMR
Yes, If you turn on a Creativision without cartridge inserted you only get a blackscreen and nothing is working... - correct again :0)
Cheers, TOM:0)
Yes, you are correct :0)
1) All gamecartridges use the internal BIOS (/ROM0 is simply connected to /ROMR on the game PCB)
2) CSL and MegaSDCart use /ROM0 for themself (to replace the internal BIOS) and give nothing back to /ROMR (or pull /ROMR high)
3) the parallel Interface divides the 16k /ROM0 romselect into 8x 2k ROM areas - uses $E800-$F000 for itself - combines the remaining 7x 2k into 1 signal and gives this signal back as /ROMR
Yes, If you turn on a Creativision without cartridge inserted you only get a blackscreen and nothing is working... - correct again :0)
Cheers, TOM:0)
http://www.8bit-homecomputermuseum.at Find me here...
Re: where the /ROMR signal is originated?
PS: The (never released) Colecovision Adapter for the Creativision would have also disabled the internal ROM (and the CPU) on a Creativision MKII...
AFAIK there is only such an adapter for the Salora Manager (using its external port) and no adapter for the Creativision... (Madrigal is working on connecting the Manager-version to the CV)
AFAIK there is only such an adapter for the Salora Manager (using its external port) and no adapter for the Creativision... (Madrigal is working on connecting the Manager-version to the CV)
http://www.8bit-homecomputermuseum.at Find me here...