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On 20 Jul 1998, James Youngman wrote: > >>>>> "ts" == Tomaz Stih <tomaz.stih@triglif.com> 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). I have seen this on a number of VMEbus boards. I seem to recall that the MVME135 and DMV152 do this. It must be a common trick. I suppose it is natural to want RAM addresses in low memory. --joel Joel Sherrill Director of Research & Development joel@OARcorp.com On-Line Applications Research Ask me about RTEMS: a free RTOS Huntsville AL 35805 Support Available (205) 722-9985