In article , peter.usenet1
@nospam.demon.co.uk says...
Proms are Harris semiconductor but I've lost the orignal chip.

I've got a Zilog MCZ 1/05 development system. A memory decode prom on
the 12/48K memory card (fitted with max 3x16K banks other 16k for 64k
is on CPU card) has blown and was running hot.

About 10 years ago I made a decoder from TTL but it's 5 chips on a
board attached to the socket by a flying lead. I've tried to
reconfigure the memory so it bank switches the monitor EPROM for
memory on the CPU card thus reducing the decode to a simple A14 and
A15 bank select on the 48k card but hit a race problem.

I'd like something that can mounted on the socket instead of a card.
Any ideas on lower chip count replacement? Even PIC or amtel if it can
decode the 5 input lines and select the memory bank in 20ns

Are you sure it wasn't a 32 X 8 ?
I have/remember 256 X 4 and 1024 X 4, but I haven't seen any 32 X 4.
I have both the open collector and the tristate versions of the 32 X 8
BPROMs and I can program them too.

Here is a pinout of the 32 X 8 :

http://www.datasheetcatalog.org/data...ips/82S123.pdf