Native, 8-port, 16-port, and third-party controllers

Native port (S1 or S2), 8-port, and 16-port controllers do not provide hardware support for terminal-attached printers, and the hardware support for third-party controllers is unknown. As a result, print files must be split into small data blocks.

The mc5 control sequence precedes each data block, which is in turn followed by the mc4 control sequence. When the terminal receives the mc5 control sequence, all subsequent data is routed to the AUX port until an mc4 control sequence is received.

Data blocks sent to the terminal must be kept relatively small. Sending too many characters to the tty at once can cause output to the printer to be mixed with the echo of what is typed during the sending operation. A delay time between data block transmissions must also be established to minimize data reception errors.

Native port, 8-port, 16-port, and third-party controllers have the following virtual printer attributes for specifying block size and delay value. These attributes are specified in a file.