Parallel interfaces with technical details.
 
Data port is address where a value must be OUTed, to set the 7bit or 8bit parallel lines that send byte to printer. Busy line is feedback from printer - when set to high voltage (1), printing cannot be continued (BUSY), low voltage (0) means printer is ready to receive byres (READY). Strobe line also goes to printer - when set low voltage (0), the data is valid and printer should take byte from data lines; when high voltage (1) - printer ignores value on data lines.
Busy and strobe lines can be inverted in interface or not (when not inverted: busy when =1, strobe when =0). Strobe is "auto" when ganerated by hardware and activated by writing to data port. Only busy and strobe lines are available unless noted otherwise. When port address is shown as two hexadecimal digits (e.g. #FB), the high byte doesn't matter. Otherwise all 16 bits matter (e.g. #E0BF). The "n" means device number (interface supports several parallel ports).