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This little hardware is propably the most curious helper-hardware I have ever built.
What it does is simple - it "emulates" a conventional 27C128 EPROM using a SRAM. The SRAM's data is buffered using a 1F GoldCap capacitor. The signals /OE, /WE and /CS are pulled up using pull-up-resistors to force the Standby-mode of the SRAM.
As I have used a 62256-SRAM, which has the double memory size of the emulated EPROM, I also added a "bank selector" switch which allows to use two different banks of SRAM memory.
The usage of this device is simple: You put the whole thing into a conventional microcontroller system in form of a SRAM unit. Alternatively, it is possible to put it into a EPROM socket and connect the /WE-signal to the system memory's /WE-signal. In this environment, you can write the needed data into the SRAM memory.
Now, the emulator just has to be put into the destination application - the GoldCap buffers the contents of the memory also while the device is not connected to a power supply (up to about one week).