HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part I

4-14 PCL Job Control Commands EN
The current unit of measure setting affects all PCL Unit moves,
horizontal and vertical rectangle size, bitmap and scalable font
metrics (how the cursor moves after printing a character). The Unit of
Measure command does not affect the interpretation of binary raster
data (bitmap fonts, raster graphics or patterns).
Once the units of measure is changed, it stays in effect until another
is selected or the printer is reset. A control panel or ? E reset returns
the current unit of measure setting back to the device default setting
(300).
The units value is part of the modified print environment. As such, it is
saved and restored whenever a macro is called or an overlay invoked,
and defaulted when establishing the overlay environment in
preparation for an overlay.
Note Values out of range are mapped to the supported value with the
minimum relative error. For example, a unit selection of 4801 would
be mapped to 7200, since the relative error (0.3332) is less than the
relative error when mapped to 3600 (0.3336):
{|4801-7200| over 7200}=0.3332 < {| 4801-3600|over 3600}=0.3336
Figure 4-6 compares a 4-unit vertical and horizontal cursor move with
a unit of measure setting of 100 versus 200 units-per-inch. Note that
the cursor move distance is halved when the Units per inch is
doubled.
14801 7200–
7200
----------------------------------- 0.3332
4801 3600–
3600
--------------------------------
0.3336=<=