The COMX Printer card allows connection of parallel and serial printers. Depending on what type of printer is connected the firmware ROM is either using the parallel firmware between memory location @C000-@CFFF and the serial firmware between memory location @D000-@DFFF or the other way around.
Parallel Printer Controller
OUT 2 is used to send a byte to the printer and INP 2 for the printer status, where:
b0=1: Acknowledge Fault
b1=0: Device Busy
b2=0: Paper Empty
b3=1: Device Not Selected
Serial Printer Controller
OUT 2 is used to send a bit to the printer and INP 2 for the printer status and to start a new range of bits for the next byte.
b0-5: Number of stop bits.
b6: If 1 special characters will be send to the printer, if 0 the hex value will be send.
b7: TV bit, if 1 the text to be printed will also be shown on the TV screen.
b0-3: Indicate the number of bits, 5, 7 or 8.
b4: If 1 parity will be send
b5: If 1 even parity (ignored if b4 = 0)
b6: If 1 no line feed to the printer
Pause after return in multiple of 10 ms.