address decoding ?

[stumpy]

Hello,
Help !......Help !.......I have two-off 2732 eproms which i want to put into one 2764 eprom. The code is not laid out as odd and even byte, it is simply the low half on one eprom and the high half on the other. A0 to A11 address the two eproms and A12 and A14, via three nand gates select the appropriate chip by providing an active-low OE for one chip exclusively. I have dumped the two eproms onto a 2764 and attempted to use the A12 and A14 decoding lines via an invertor to send the extra address line on the 2764 (a12) into a high state so as to access the code in the high block. This is obviously not the correct way to do it as i cannot get the code to start running !!........Can anyone put me right here as i cannot see another way to do it. I have also tried dumping the blocks onto the 2764 the opposite way around, but alas, no luck !!
Regards, stumpy.

[Simon (Webmaster)]

Hi

You say A12 and A14 - is A13 not used?

[nigelwright7557]

It wont work because the two eproms have seperate CS (chip select lines).

You need to AND these together and apply them to the new eprom.

You are right to add the extra address line.