If there is a problem transferring data between the computer and the printer, try placing the printer in Communications Diagnostics mode. The printer will print the ASCII characters and their respective hexadecimal values for any data received from the host computer:
To enter diagnostic mode, do one of the following:
Send the ZPL
~JD
command- to the printer. (See the ZPL Programming Guide.)
Send the EPL
dump
command to the printer. (See the EPL Programming Guide.)