Star LC-90 User Manual page 54

48 Troubleshooting
Begin printing from your computer,
Instead of a normal printout, data will be printed in sixteen columns of
hexadecimal numbers (two groups of eight numbers each). The equivalent
printalble characters (or dots in the case of unprintable codes) are printed to
the right of each row of hexadecimal numbers.
After you start the hexadecimal dump (by using the procedure described
above), you can switch it off (and return the printer to normal operation) by
holding down the control panel's Power button.