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5200 Chip Select and Addressing Logic


cschell

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Ok, some questions for the 5200 gurus on 5200 cartridge hardware.

 

The faq pinouts show it has two "enable" lines, 40-7F and 80-BF. As I don't have a 5200 PCB to comparison, I figured I ask about these.

 

Are they active low? Or high? Assuming they're active low, that means I would enable the EPROM when either went low (32K game of course.) Would I then connect the 40-7F line to A15 of the eprom? That would mean that when 40-7F enable went low, the eprom would be active and the lower half of its contents would be selected.

 

The next question after I get this sorted out will be: What's the format for BBSB bankswitching?

 

Thanks,

Chad

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This looks like it will be a very short lived mulling anyway. Again Atari failed to bring either the clock or r/w line to the cartridge port. This means that once again, it would be a pain to get modern high speed parts to successfully perform RAM writes if the cart were to load games "in system."

 

As I'm not 5200 fan I just can't motivate myself to deal with that hassle for this platform.

 

The other option would be just to load games from the PC into NVRAM and stuff the cart into the 5200 preloaded. Of course that's just an eprom emulator, not very exciting or unique. Also hard to justify the cost of a PLD or MCU or both on board to accomplish something other than parallel port loading and BBSB support.

 

Chad

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Both.  :D

 

But I'm not. ;)

 

Bounty Bob Bankswitching:

- Four 4 KB banks (A,B,C,D) are mapped into $4000-$4FFF. An access to $4FF6

selects bank A, $4FF7 - bank B, $4FF8 - bank C, $4FF9 - bank D.

- Four 4 KB banks (E,F,G,H) are mapped into $5000-$5FFF. An access to $5FF6

selects bank E, $5FF7 - bank F, $5FF8 - bank G, $5FF9 - bank H.

- The remaining 8 KB is mapped to upper 16 KB of cartridge address space

in Atari 5200. That is, $8000-$9FFF and $A000-$BFFF contain same data.

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