I've looked at doing the keyboard a bit, and it's a little more involved than just putting key codes out on a serial port.
It is my understanding the 8049 has an internal non-reprogrammble ROM. There's a pin to hold high telling it to use an external ROM for development. So for our uses, we'd need an external ROM. The way it accesses the external ROM is via an 8 bit bus that puts the address being fetched on the bus and pulses the address latch enable (ALE) line, then pulses /PSEN to put the data on the bus. I'm not aware of a ROM that behaves that way, so to use it with something like a 27C256 or similar, you'd need additional logic to latch the bus data when ALE is asserted, and feed that to the ROM, then attach /PSEN to /OE of the ROM?
The 8021 had no provision for an external or reprogrammable ROM, it was factory programmed and that's it.
It is my understanding the 8049 has an internal non-reprogrammble ROM. There's a pin to hold high telling it to use an external ROM for development. So for our uses, we'd need an external ROM. The way it accesses the external ROM is via an 8 bit bus that puts the address being fetched on the bus and pulses the address latch enable (ALE) line, then pulses /PSEN to put the data on the bus. I'm not aware of a ROM that behaves that way, so to use it with something like a 27C256 or similar, you'd need additional logic to latch the bus data when ALE is asserted, and feed that to the ROM, then attach /PSEN to /OE of the ROM?
The 8021 had no provision for an external or reprogrammable ROM, it was factory programmed and that's it.