Siemens SINUMERIK 840D sl Function Manual page 538

Detailed description
2.12 Block search
Explanation of example
If the number of spindles is known, outputs of the same type can be written in one part
program block to reduce program runtime.
Output of $P_SEARCH_SDIR should be made in a separate part program block because
spindle positioning or switchover to axis mode in conjunction with the gear change can
cause an alarm.
Control response for REPOS
If the started ASUB is ended with REPOSA, spindle 1 remains at position 111 degrees, while
spindle 2 is repositioned at position 77 degrees.
If a different response is required, the program sequence for block search (for example)
"N05 M3 S..." and "N30 SPOS[2] = IC(...)" requires special treatment.
Whether block search is active can be ascertained in the ASUB via the system variable
$P_SEARCH.
$P_SEARCH == 1 ; Block search active
In the case of incremental positioning after speed control operation, the path to be traversed
is defined but, in some cases, the final position reached only becomes known during
positioning. This is the case, for example, during position calibration on crossing the zero
mark when switching on position control. For this reason, the distance programmed after the
zero position is accepted as the REPOS position (REPOSA in the ASUB).
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Basic logic functions: Auxiliary Function Output to PLC (H2)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0