HP Color LaserJet 5500 Technical Reference Manual page 179

Example Summary
The FSDOWNLOAD command downloads data to printers
which support this command. This command allows data to
be downloaded to either the printers internal disk (such as
available in HP LaserJet 4000 series, 5Si, 5SiMx, and 5Si
Mopier printers) or flash memory (such as available in HP
LaserJet 5, 5M, and 4000 series printers).
To identify what is stored on the disk or in flash memory,
you can print a directory listing for that memory device.
This directory listing identifies all directories, file names,
and file sizes. A directory listing can be printed from the
printer's control panel by selecting either the Disk
Directory page or the Flash Directory page in the Test
menu.
Note
A file system command sequence can be typed in a text
editor and copied to the printer, but there are some places
where binary data needs to be sent. This is not a problem
as long as there is an ASCII character equivalent to the
necessary decimal value. For example, the decimal value
for Escape is 027. There is an ASCII character ( ) for this
decimal value, thus it can be typed in a text editor.
There might be times when a text editor will not allow you
to type a character with a certain decimal value. For
example, you might need to send the character whose
decimal value is 000. There is no ASCII character for that
value, thus a text editor will not allow you to send this byte
to the printer.
PJL File System Commands 9-17