Siemens SINUMERIK 840D sl Function Manual page 686

Measurement (M5)
Setting zeros, workpiece measuring and tool measuring
8.4.5.5 Measurement of a tool length of two tools with the following orientation:
Tool orientation
Tools oriented towards the tool carrier must be marked by $AC_MEAS_TOOL_MASK =
0x200. The calculated tool lengths are then included negatively.
Two turning tools each with their own reference point with a tool orientation in the approach direction
In the case of the tool position of two turning 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
686
Approach direction and tool orientation -x
$AC_MEAS_TOOL_MASK = 0x40
$AC_MEAS_DIR_APPROACH = 1
Function Manual, 03/2009, 6FC5397-1BP10-4BA0
Extended Functions