Casio CZ/ VZ/ FZ - Pro Series

>I just got sent a photo of a ROM card opened up. There is not much
>difference with the RAM and ROM PCB, the RAM has more etchings and
>tracks in it for an extra chip that does switching of the CE (Chip
>Enable) pin, and also the WE (Write Enable) pin, both of which the
>ROM doesn't need. And a few other differences in the pin track
>layouts to the RAM chip, but that's it. I've uploaded a schematic for
>the RAM card in the FILES section on this site.

I think that was probably my ROM card, actually.

>Regarding having a larger chip, the schematics show already that it
>was made to accommodate a chip 2x as large as the one used, there is
>a spare address line not used on the connector. This is for the ROM
>chip, which is 2x larger than the RAM chip (which is why it has an
>extra bank of sounds) - The ROM is 512k and the RAM is 256k. It would
>require no more effort than dropping in a 512k RAM chip and hooking
>up the extra address line. As you say, an even larger chip can be
>installed and the highest address lines switched with a DIP switch to
>get extra banks.

Referring to the service manual... apparently a 2-bank RAM card was never 
released.  When the VZ detects a RAM card, the highest address bit is 
disabled (unless someone wants to modify the OS).  To access both banks (as 
it would be useful to have 192 online patches), the VZ needs to detect a ROM 
card.  In this mode, it would be impossible to write patches, and likely it 
would have to be switched off when changing this to avoid crashing things.  
But, if it can be determined how the VZ detects the card type, it could make 
things a little more interesting.  From the diagram, it seems like only the 
CD (Card Detect?) pin could determine this... but my scan only shows the 
component side of the board, and that pin connects to something on the other 
side.  This pin is grounded for a RAM card, so inside the VZ it's probably 
just pulling down a high value.  But if that's the case, I'm not sure what a 
ROM card could do differently.... I can take my card apart again if 
necessary (though it's sort of damaged enough already...)

Actually, maybe this should be verified.  If anyone has a RAM card, I would 
appreciate it if this could be tested:  When a RAM card is inserted and the 
CARD button is pressed multiple times, does it switch banks between CARD (1) 
and CARD (2)?  If it does, that means it is actually using the highest 
address bit, but since it's not connected, it's still just looking at the 
same data.  Seems like it would be bad design to do it this way, but it's 
possible.  I suspect a RAM card just shows up as CARD, with no indication of 
bank.

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