Expansion port on 72 pin cart connector. Has it been used?

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doragasu
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Expansion port on 72 pin cart connector. Has it been used?

Post by doragasu » Sun Apr 24, 2016 10:16 am

While designing my MMC3 cart I thought of using the pins of the expansion port (16 ~ 20 and 51 ~ 55) for the CPLD JTAG port and the #WE of the flash chips. But I don't know if these pins are used by any peripherals that might make my cart go nuts.

Any info about this?

lidnariq
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Re: Expansion port on 72 pin cart connector. Has it been use

Post by lidnariq » Sun Apr 24, 2016 10:45 am

The only official use of the EXP pins is as documented on the wiki, and this (underdocumented, unused) test cart.

The various in-place flashable carts I've seen have been making use of the EXP pins for programming, but I don't know if there's any documented conventions.

Note that INL's carts add a separate card-edge connector for JTAG for the CPLD.

doragasu
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Re: Expansion port on 72 pin cart connector. Has it been use

Post by doragasu » Sun Apr 24, 2016 1:42 pm

Thanks for the fast and complete answer! It looks like as long as I do not use EXP 0, 2, 5, 6 and 9, there should be no problem.

zzo38
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Re: Expansion port on 72 pin cart connector. Has it been use

Post by zzo38 » Mon Apr 25, 2016 12:05 am

As long as the expansion devices aren't permanently connected, I would expect that you could probably use EXP 5 as well if you need another pin (in case five extra pins isn't enough), since it may be consider as a cartridge-specific features, so you could use it for your own purposes as well. (However, I am not quite sure; if other people understand then it could be answered better?)
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doragasu
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Re: Expansion port on 72 pin cart connector. Has it been use

Post by doragasu » Mon Apr 25, 2016 2:07 am

Nice suggestion, thanks!

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Memblers
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Re: Expansion port on 72 pin cart connector. Has it been use

Post by Memblers » Mon Apr 25, 2016 2:34 am

My GTROM board uses EXP4 for programming the lockout chip, but it's done through an extra connector which is basically a jumper and is only installed during programming.

This is not widely used, but here are the EXP pin definitions I've used on the 8TROM board. Probably pretty close to what I'll use in the future. It was to be compatible with the ENIO CPU board.

Code: Select all

EXP0 - CopyNES mapper disable
EXP1 - CAN bus +
EXP2 - PRG A0
EXP3 - PRG A1
EXP4 - PRG A2
EXP5 - EXP /CE
EXP6 - PowerPak sound mod
EXP7 - ?
EXP8 - CAN bus -
EXP9 - PRG R/W

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