Siemens SINUMERIK 840D sl Function Manual page 667

Two milling tools each with their own reference point with a tool orientation in the approach direction
In the case of the tool position of two milling tools each with their own reference point, not
only are the input variables of measurement type 23 evaluated but also the values of the
following input variables:
Approach direction and tool orientation +x
$AC_MEAS_TOOL_MASK = 0x2
$AC_MEAS_DIR_APPROACH = 0
Extended Functions
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
8.4 Setting zeros, workpiece measuring and tool measuring
Approach direction and tool orientation -x
$AC_MEAS_TOOL_MASK = 0x40
$AC_MEAS_DIR_APPROACH = 1
Measurement (M5)
667