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jdgabbard

Question on MSX Cartridge Signals

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Not sure if anyone here has the knowledge to have a discussion on a technical level concerning the MSX standard.  But I have a few questions concerning the various slot signals.

 

1) I see very few references to the SW1 & SW2 signals, other than they should be connected together on the cartridge pcb.  However, no mention of where they go, or what they do.  I'm assuming that there is some bit in some register set or reset.  But I can't find any reference to it.  Anyone have any idea?

 

2) As far as CS1, CS2, and CS12, I am assuming that these three select lines function independent of individual slots?  I.e., they should be active on all slots at the same time, and not gated to specific slots?

 

3) SLTSL seems fairly easy to generate.  My understanding is that the register A8h provides the 2-bit slot number for pages 0-3 of the 64k of memory.  So I should be able to use a 1-to-4 decode on A15 & A14 to create my page select lines, and then just gate them properly with the A8h register to have the possible outcomes.  (Been working on a truth table, but it going to be fairly extensive.  This could probably be implemented with a fairly fast EEPROM for the logic).  I understand how the decode works I think.  I just want to verify I am not missing anything here.  Any traps for noobs?

 

If you're wanting more information as to the scope of what I'm doing, I am designing an expansion adapter for my MSX1 to open up Slots 2 & 3, possibly decoding one to the 4 secondary slots.

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I just implemented a feature on my GR8BIT this weekend that uses the cartridge SW1 and SW2 feature. 

 

There was a Yamaha machine that also did. 

 

It provided insert protection. A normally closed switch in the slot housing disconnects when a cartridge is inserting, and then those pins re-connect the signal when the cartridge is in. The 4th contact on the cartridge is recessed to create contact only after the cartridge is aligned. 

 

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