Im currently looking at some SFC carts and noticed the normally PAL used for the CS of each chip missing...does every chip (aka ROM Chips & add-ons like DSP) have they own CS logic (and so being hard-addressed) or is it handled somehow else? BTW : Does somebody have the pinout of the 16/32 M 44 pin chips? Or could somebody point me to someone who knows about it?
Nintendo doesn't use PALs. I don't understand what you're asking. /CS is provided on the connector and decoded on cart only if the board requires it (multiple ROMs or whatever.)
I explained myself wrong. /CS is one signal for all chips. How does the system discriminate which chip its reading from /writing to (in case of the SRAM)?
No idea how the SNES does it, but usually this is controlled by one of the upper address lines, either by connecting it to /CS or /OE. If the address-line is high then one pair of ROMs (for 8-bit ROMs and a 16-bit bus) gets to output its data and if it's low then the other one does. They can all be selected at the same time but with only one (or one pair) active on the bus... Stone
Just to clarify, SNES has an 8-bit data bus. It provides /CS for YOU to decode, games with multiple ROMs do this many different ways. One can use a MAD-1 (up to two ROMs IIRC) or simply a 2:4 decoder (74139) or whatever you wish.
D'oh, yes, sorry, I forgot about the SNES's short bus I was thinking of the Robotron 2084 ROM board which uses a 74154 to convert 4 address lines into 16 /CS signals (though only 12 are used). Stone
