This command compares the contents of a specified GPRM register
to a value in one of the following:
1) another GPRM, or
2) an SPRM register, or
3) a specified constant.
If the result of the comparison is True, this command then computes
a new value for another specified GPRM register (by performing the
Set GPRM operations
with one of the following sources):
1) another GPRM register,
2)
a 16-bit constant value.
The Link command is always executed regardless of
the result of the comparison.
The Link command can optionally highlight a specified menu button.