"Bill Sudbrink" <bill(a)chipware.com> wrote: No, you don't need anything there. Here is the sequence that is done: 1. Examine Switch 2. Place 0C3h on data cable to processor board 3. Step processor one cycle 4. Place Low address switches on cable to processor board 5. Step processor one cycle 6. Place High address switches on cable to processor board 7. Step processor one cycle 8. Processor places address on address bus and is holding for data from RAM to execute. You'll notice that the key here is that the cable is most important to be correct. The picture you had with the complete switch to address mapping showed that the data signals from the front panel to the processor were swapped on a byte basis, 0-7 swapped 7-0. Like I said, the reason it seem to work at all is because swapping the bits of 0C3h is 0C3h. When you inverted the plug and it didn't work, it was because it was then sending something other than 0C3h to the processor. Like I said, it is 0-7 and 7-0 that is swapped. There may be other issues as well but I'll have to look at the schematics before I can say exactly what I think is the entire issue. Dwight