Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 715)

Paramacros
Chapter 28
28-15
The common parameters refer to parameter numbers 100 to 199 and 500 to
999 for all 9/Series controls except for the 9/240, which allows 100 to 199
and 500 to 699. The common parameters are assigned through the use of a
common parameter table as described on page 28-41.
Common parameters are global in nature. This means that the same set of
parameters can be called by any program, macro, subprogram, or MDI
program.
Common parameters are divided in to two types: saved or unsaved.
Saved common parameters refers to the common parameters that retain
their value even after power to the control is lost. Saved common
parameters are parameter numbers 500 - 999 for all 9/Series controls
except the 9/240, which allows only 500 to 699.
Unsaved common parameters refers to the common parameters that do
not retain their value after power to the control is lost. When power to
the control is turned back on, these parameters reset their value to zero.
Unsaved common parameters are numbers 100 - 199.
The PAL programmer can use some of these parameters to check
parametric values with the Paramacro Range Check feature. For more
information refer to the description of $PRMQTY and $PRMERR in your
9/Series CNC PAL Reference Manual.
System parameters may be used by any part program, including
paramacros and subprograms. All of these parameters may be used as data
or may be changed by assignment (read and write) unless indicated
differently in Table 28.D.
These system parameters are generated by the control and can be modified
by operation or programming. They correspond to different control
conditions such as current operating modes, offsets, etc.
Table 28.D lists the system parameters.
28.4.2
Common Parameters
28.4.3
System Parameters