Servo control
4.20 Central probe evaluation
Drive functions
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
183
Common features for central measuring with and without handshake
Both measuring procedures have the following points in common:
● Setting the input terminal in p0680.
● Signal source, synchronization signal in p0681.
● Signal source, control word probe p0682.
● Transfer with the communication interface PROFIdrive.
● Synchronizing and monitoring isochronous PROFIdrive
● Prerequisite for measurements is the synchronization between the control and drive.
● Setpoint transfer at start time To and actual value transfer at instant in time Ti in the
PROFIBUS cycle (max. 8 ms).
● Time stamp: Format (drive increments, NC decrements)
● Each valid time stamp in the drive is incremented by 1 in order to make a differentiation
between a valid measuring time zero and an invalid time format. This increment is
removed again by the higher-level control.
● The value "0" in the interface is an invalid time format and indicates that a measured
value is not available.
● Sequencer for the control/status word processing
● Monitoring functions (sign of life)
● Faults
Note
Time-critical data transfer
The status information E_DIGITAL and A_DIGITAL in telegrams 39x are not subject to any
precise time restraints according to the specifications. The transfer of E_DIGITAL and the
output of A_DIGITAL are realized independently of the PROFIBUS cycle wi
th the
PROFIdrive PZD sampling time according to p2048. Depending on the module, this can be
set to between 1 ms and 16 ms. As a consequence, dead times must be expected for the
transfer of output values and the feedback signal of input values.
e probe status word MT_ZSW is identical with the content of E_DIGITAL, it is
however directly transferred in PZDs. As a consequence, for time
-critical applications
measuring probes or cams should be used.
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