n is the number of the NV bit image (defined using the FS q command).
m specifies the bit image mode.
NV bit image is a bit image defined in non-volatile memory by FS q and
printed by FS p.
This command is not effective when the specified NV bit image has not been
defined.
In standard mode, this command is effective only when there is no data in the
print buffer.
This command is not affected by print modes (emphasized, underline,
character size, white/black reverse printing, or 90° rotated characters, etc.),
except upside-down printing mode.
If the downloaded bit-image to be printed exceeds one line, the excess data is
not printed.