PAL unused address space

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Ronny Ribeiro

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Jan 29, 2024, 9:03:08 AMJan 29
to PAL 6502 computer
Hello, everyone!

A while ago I noticed some memory space not mapped in the PAL memory space.
There is 768 bytes between $1400 and $1700 and It occurred me to map an ACIA adapter there, or something else. For an ACIA I would go with a very compact board using a CPLD like a 22V10 type. I could use the rest to map a small ROM, again using a 22V10, to house a wozmon to work in tandem with the ACIA.
Does any one know of any hindrance to map that chunk of address space? I could breadboard everything and discover by myself, which I would eventually do, but there is a lot of other things that I would like to breadboard instead.
Thanks for any information.
Best Regards,

Ronny

Hans Otten

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Jan 29, 2024, 9:20:41 AMJan 29
to PAL 6502 computer
That area is fine for I/O. The Corsham Clone has a 6850 based ACIA mapped in the 1600 space with very little address decoding logic required.

Ronny Ribeiro

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Jan 29, 2024, 11:13:06 AMJan 29
to Hans Otten, PAL 6502 computer
Thanks Hans, good to know :)
I'm gonna go for a small footprint, as shown in the attached picture.
I'll report the results here when I have it done.
Regards,

Ronny

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