I buitl an adapter to use 64/128/256 eproms with the ECM. Id like to be able to fill these chips with different images and select between them. I have been able to find references on similar applications, but no real information regarding it.
for example:
a 27256 is 32kbytes. = 8 positions
so you have
000 - 0fff image 1
1000 - 1fff image 2
2000 - 2fff image 3
3000 - 3fff image 4
4000 - 4fff image 5
5000 - 5fff image 6
6000 - 6fff image 7
7000 - 7fff image 8
the difference with 256 and 32 is the address lines.. 3 extra.
A12, A13 and A14.
I have it so VCC and VPP are jumped together. A12/13(128) and 14(256) are grouned.
If i use a 64 or 128 I have VCC, VPP and PGM jumpered.
how do you select them ranges!? the most quick and dirty method?
TIA
for example:
a 27256 is 32kbytes. = 8 positions
so you have
000 - 0fff image 1
1000 - 1fff image 2
2000 - 2fff image 3
3000 - 3fff image 4
4000 - 4fff image 5
5000 - 5fff image 6
6000 - 6fff image 7
7000 - 7fff image 8
the difference with 256 and 32 is the address lines.. 3 extra.
A12, A13 and A14.
I have it so VCC and VPP are jumped together. A12/13(128) and 14(256) are grouned.
If i use a 64 or 128 I have VCC, VPP and PGM jumpered.
how do you select them ranges!? the most quick and dirty method?
TIA
