... at least a simulator that simulates the MCU and the external logic. There are numerous 805x simulators, though few or none will actually simulate the DS89C4xx-series, though it's really not difficult, just tedious, to write a simulator. Finding a simulator that will simulate all the possible external logic might be even more difficult, these days, as few people use "family" (74Txxx, where T is the technology, and xxx the part number) logic any longer. If you can write an accurate MCU description for your testbench, you can WRITE a simulation of the bus transactions, and other functions you see yourself using, in VHDL, or, if "close but no cigar" is good enough, you can use one of the several 805x cores in VHDL or Verilog as a basis and attempt to write a testbench that executes your program from a file. I don't see that as going very quickly either, though. Once you have that, you use the testbench to stimulate your external logic in a CPLD. There ARE simulators that might help you with that, and they're free, so to speak, from XILINX, Altera, Lattice, and others. You may find that the CPLD is also a lower-cost solution to your logic problem.

RE