Hi MIKE,

On 04-Jan-03, MIKE ROSS wrote to Greg Mayman:

 RJT>> Yes indeed,  though I still want to make an EPROM emulator...

 GM>> CMOS RAM chip plus a backup battery, sitting in a wirewrap
 GM>> socket. It usually needs a couple of extra components, such as
 GM>> isolation diodes on the Vpp, and a write enable switch.

Or even just buy a battery backed CMOS RAM module designed to emulate
an EPROM. They do exist, I've bought and used them...

 MR> I could never understand the point of an Eprom emulator. I mean if
 MR> the program works why not simply burn the eprom and be done with
 MR> it. If it has a bug then simply erase the eprom and start again.
 MR> Why the need for an emulator that may cost hundreds of dollars?

Because, in the field you can have generic software that needs to the
"trimmed" for some applications (like setting the change points for a
transmission). With an emulator and knowledge of what values to put in
appropriate tables in the emulated PROM you can trim the settings to
suit the specific application. If you do this with EPROMS, sure you
can change them, but it takes a long time to test various combinations
of settings. Often settings were specific to an operator, to suit the
specific terrain of their area. If you have an emulator you can blow
the final settings into EPROM to leave in the test unit and for the
reference PROM to take back to the factory.

George

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