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On 20 Jul 1998, James Youngman wrote: > >>>>> "ts" == Tomaz Stih <firstname.lastname@example.org> writes: > > ts> When dealing with 68000 boards with no vector base register > ts> there is a problem with setting vectors because it is common > ts> to put ROM at 0x0000 address where vectors reside thus making > ts> it impossible to change them. > > 00000000 does not have to be ROM. You just have to be able to load 8 > bytes from it at reset time. I've seen boards by Pro-Active Control > which use a counter to change the memory mapping after the right > number of bus cycles to that the vectors can be in RAM (except, > effectively, the reset vector). It easier than this. All you need to do is map the ROM at both its correct address and at address 0 from reset until the first processor write. If you don't want supervisor code in RAM, you could also permanently map the ROM at address 0 in the Supervisor Program Space. Peter -- Peter Jeremy (VK2PJ) email@example.com Alcatel Australia Limited 41 Mandible St Phone: +61 2 9690 5019 ALEXANDRIA NSW 2015 Fax: +61 2 9690 5247