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Prototype #2 is aliiiive!


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8 hours ago, TomXP411 said:

I think that all of the CS lines will be present on each card slot, which makes it up to the expansion device to operate on the correct CS pin. 

This will probably mean a jumper block on the card, which connects to the correct pin on the slot. Someone could devise a PnP system that sets the correct CS line through software, but I don't see much utility in that when a 10-pin jumper block costs next to nothing.

 

 

Simple cards would still be simpler if there is one device space associated per card and one handed to all of them. And that is less like to give conflicts where some card makers take shortcuts on which space their drivers address ... having the dedicated select be at card slot +3 (4-7) means they should write their driver for whichever slot it is put into.

BUT it's not a major issue, and this design makes a single slot and optional riser board straightforward for the small form factor CX16e.

 

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On 1/8/2021 at 11:39 PM, BruceMcF said:

Simple cards would still be simpler if there is one device space associated per card and one handed to all of them. And that is less like to give conflicts where some card makers take shortcuts on which space their drivers address ... having the dedicated select be at card slot +3 (4-7) means they should write their driver for whichever slot it is put into.

BUT it's not a major issue, and this design makes a single slot and optional riser board straightforward for the small form factor CX16e.

 

You're not wrong, but there's always going to be That One Guy who takes the shortcut... 

anyway, I'm basing my assumption on this pinout diagram from Facebook:

 

I'm assuming that IO3-IO7 are active low when the system is addressing the expansion port I/O range. 

 

 

expansion port.jpg

Edited by TomXP411
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Yes, I didn't have time to look the card spec up because of the exam my MBA students just took, but I read it the same way .... I'd assume from a 3 to 8 pulldown decoder with i0-i2 on a5-a7, with o0-o2 used internally. That can be pretty flat logic.

There was a time in the late 90s when I was perusing glue logic data sheets for a piece of C64 kit I never got around to building, it was well after the days of TTL, but from the TTL days pull down selects were popular because TTL pulled down harder than it pulled up. CMOS is more symmetric.

 

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