Siemens SIMATIC S5 Manual page 217

The Standard Function Block FB164
For more detailed information about the significance of the parameters in the individual modes,
refer to Part 4 "Functions".
The actual position, and the distance to go are updated in the axis DB regardless of how parame-
ters are assigned to FBI 64 (direct or indirect parameter assignment).
Only when indirect parameter assignment is selected and byte DR7 (corresponds to the parame-
ter BCD) is not zero, are these values in BCD format in the axis DB. When direct parameter as-
signment is selected and the parameter BCD is a"1" signal, one of these values (BA 71 ...73) is
available at the output parameter ANZG (ANZ1/ANZ2 for the S5-1 15U) ofFB164 in BCD repre-
sentation, however, the value is stored in binary in the axis DB.
Data words DW n+l 1 (axis mode, current M function) and DW n+12 (checkback signals from
the axis, error message from the axis) of the axis DB are only updated with indirect parameter as-
signment, With direct parameter assignment they have the value KHOOOO.
The error message byte DR n+12 of the axis DB is identical to flag byte FY251 (=> Section 7.2
"Troubleshooting"),
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