This is the classic Arduino.  8 bits architecture is required to keep things as simple as possible - just because the PERTEC communication protocol is a real pain. It is documented on bitsavers on all those PDFs gathered by the willpower of our digital forefathers. Documenting this is still work in progress, as I have to read everything from beginning to end. Some PDFs have hidden surprises which the rest do not tell. These secrets are well kept.

Added 512kB RAM for buffering the transfer.