I have married the DS80C320 with a Coolrunner XCR3128 and it works nice.

The XCR128 does all needed logic (address latch, address decoding, memory switching, I/O expansion). Because the DS80C320 runs at 32MHz it was difficult to get such fast EPROM devices. To be fast enough I use only a fast cache SRAM device (KM681001), which provide 64kB code and 64kB data space.

To start an application the XCR3128 contain a little truth table, wich was activated after every access over PSEN from address 0x0000 (reset vector). This truth table contain a small routine to download a 4kB boot loader from a 24C512 into the SRAM at 0xF000 and jump to it.

The 24C512 was also connected to the XCR3128, so no additional port pins needed and also the application was unable to alter the content of the 24C512 accidentally.

All access to the 24C512 was only possible from addresses above 0xF000 (the boot loader area) and also all writing to the 64kB code space on the SRAM.



Peter