Mega2560 as eprom emulator

I am wanting to use my Mega2560 as an eprom emulator. Is it possible to allow an external microcontroller to access the mega's internal eprom and allow real-time changes to the eprom whe in use by the ext mcu?


{If you want to build an EPROM emulator, you use a corresponding RAM chip with battery backup. If you want quasi-simultaneous access, you have to provide two-way buffers and the logic to control them. I suppose an ATMega could be practical as part of the control circuitry for this.}

You need to dual-port some RAM with tri-state buffers (or clever use of the CPUs’ pins). It’s easy enough so if you decide to proceed we can talk about it.


You could probably emulate a really SLOW EPROM wholly in software. Say, 4us access time.