Epson 420i - Manual (Page 83)

APPENDIX
INPUT DATA DUMP IN HEXADECIMAL
There is a function of printing input data from a computer in hexadeciamal codes.
Therefore, it is possible to check the data the printer has received. To perform this
function, keep pushing both the LF and the FF switches at power-on till the initializa-
tion operation ends. Hereafter, 16 bytes of input data will be printed a line at a time
due to the function of the automatic printing provided. If the number of input data
is less than 16 bytes and it is necessary to print them all, press the ON-LINE switch.
After printing, push the ON-LINE switch again to return to the dump function from
the OFF-LINE state. This function can be terminated by either of the 3 ways shown
below.
(1) Turn power off, wait 2 seconds and then turn it back on again.
(2) Push the RESET switch.
(3) Input the INITIAL signal.
77