29 Jul
2004
29 Jul
'04
12:05 p.m.
From: "John Honniball"
<coredump(a)gifford.co.uk>
Jay West wrote:
Hi John
Most of the applications Jay is talking about require faster
than 100ns someplace. Most EPROMs just are not in that range.
Dwight
Since the blank chips are nigh impossible to find
anymore... is it possible
to use something like a PIC chip on a small DIP carrier card, that could be
plugged into an existing loader rom or microcode rom socket and function
just like the "real thing" to the system?
You wouldn't use a PIC chip for something like this. A PIC would be
used in a microcontroller-type application, where program-controlled
behaviour is required. To replace a ROM, we could simply use another
ROM (or PROM, EPROM, EEPROM, Flash ROM, etc.) with a pinout adaptor.
People are already doing this for PROMs in mobile radios. These PROMs
are in fact the same chips as one finds in a PDP-11 for booting (M9312)
and for storing the 8008 firmware in an 11/34 console card. The
PROMs in question are 82S131, 74S571 or Am27S13 types (512x8). I have
some blanks here to fix a console card, as it happens.
Scroll down here:
http://www.open.org/~blenderm/syntorx/legacy.html
to the section headed "EPROM Conversion" to read about the PROM
replacements for Syntor radios. And see this page:
http://www.open.org/~blenderm/syntorx/legacyeprom.html
for photos of a completed adaptor.
Do you know the chip numbers and/or specs for the ROMs you wish to
emulate?
--
John Honniball
coredump(a)gifford.co.uk