EPROM emulator

[jgwynne at mrcday.com]

   In message <36C30574.D749C80B at cruzers.com>, you write:
 
| This sounds like you're thinking of something that plugs into an EPROM
| socket and is independent of the target system.

yes

| Instead, how about a board with RAM and logic that plugs between a
| MEMCAL and a P4 ECM - which uses the P4's CPU and ALDL commands to write
| to the RAM.  The MEMCAL doesn't get the processor R/~W signal, but I've
| come up with a jumperless solution using a medium sized EPLD.  Of
| course, any ALDL based design requires a custom code fragment in the
| EPROM.  This may reduce the usefulness of such a board.

but if you are going to make a board anyways, why not just make it
general purpose and not require any custom code fragments. I sketched up a
circuit over lunch with RAM and FLASH in two banks. Once powered, the
ecm runs out of flash until you down load your data to the RAM. You
can then switch back and fourth between the two and alter both. What's 
the largest _single chip_ used (those with two can use two boards)? 64k x 8 
(512k bits) right? 

Someone should be thinking of software to display and alter tables in
this real time mode. It would be nice to run under both windows and
Linux.

john