XC164 using external ROM

We want to place an external ROM on our dev board so that if our code exceeds flash limit we can revert to old fashioned crash & burn techniques without having to lay out a new dev board. So the question is: with EA tied low program code appears to start at 000000h. Can I simply place a contiguous 512k byte ROM there or do I have to map out the SFR locations etc?

  • Can I simply place a contiguous 512k byte ROM there

    Yes. You will not be able to access the external ROM through addresses 0x8000-0xFFFF because reads/writes to these addresses will access on-chip RAM, SFR and so on. Of course, you can access those memory locations in external ROM through other (mirrored) address areas, say 0x88000-0x8FFFF.

    - mike

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