ZX-40 Development Board?

[DH*]

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[mikep]

Very neat. A schematic would also be useful unless it is proprietary. The angled jumper J2-A is interesting.

I'm sorry to dash your hopes but support for program memory over 64K is probably hard to do because the architecture is built around 2 byte addresses. I guess some kind of paging system could be used to flip to the upper half of the EEPROM but why bother? Most ZBasic programs only use a fraction of the 32K standard EEPROM and I really cannot see anyone using more than 64K unless they have huge amounts of static array data or string data that is loaded from the EEPROM.

[DH*]

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[mikep]

I am familar with some of the history around the BX-24AHT project. The URL you gave doesn't work.

Yes the AT25HP512 is very expensive. It is a little cheaper in the SOIC-16 packaging. I haven't seen the 25LC1024 before so thanks for pointing that out.

For paired jumpers like J2-A/J2-B I have used a miniature DPDT slide switch to ensure both are changed at the same time.