We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.
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