this protocol uses the following signal lines:
1 pin 1 protective ground (pg)
2 2 transmit data (txd)
3 3 receive data (rxd) (with internal pull-up) 1)
4 5 clear to send (cts) (with internal pull-up) 1)
5 7 signal ground (sg)
6 20 data terminal ready (dtr)
the ready / busy dtr protocol uses the data terminal ready line to control the transmission of data from the host to prevent a buffer overflow.
the signal lines txd (pin 2) and cts (pin 5) are only necessary if the device status report is required (see picture "connection for unidirectional transfer mode").
cables with bridges at printer side (4 to 5) for older pms (lower than pm-40a4) can also be used!
- version 2 - connection full duplex transfer mode
control the transmission of data from the host to prevent a buffer overflow. the ready / busy dtr protocol uses the data terminal ready line to
bridge between 7 and 8 on pc side means alternative rts to cts.
additional information
after power-on dtr is activated and the printer is ready to receive data.
dtr is deactivated when the interface buffer has only space left only for 256 more characters. further incoming data will be stored until the interface buffer is full. all data sent in addition will get lost.
dtr is activated again if there is a free interface buffer space of 512 characters.
dtr is immediately deactivated, if local mode is entered.
it is activated again, if local mode is left and a minimum of 512 bytes interface buffer is available.