Siemens SIMOTION Function Manual page 141

Both edges,
rising edge first
Both edges,
Falling edge
First
5.2.4.2 Cyclic measurement (as of V3.2)
In cyclical measurement, up to two edges can be measured per processing cycle of the
measuring input TO IPO interpolation cycle clock, IPO_2 interpolation cycle clock, and servo
cycle clock in the case of TM17 High Feature, D4x5-2 (X142) and C240 (B1-B4).
In the case of D435-2 DP/PN, D445-2 DP/PN, and D455-2 DP/PN, it is also possible to
configure a processing cycle clock in Servo_fast or IPO_fast for the measuring input.
In the onboard measuring inputs of D4xx, D410-2, D4x5-2 (X122/X132), CX32, CX32-2,
CU310/310-2/320/320-2, the minimum duration between two measurements is three servo
cycles. Measuring signals in between are not detected.
Measurements are taken cyclically, until they are terminated with a command.
The measured values must be read from the user program in good time before they are
overwritten by a new measurement.
Note
Cyclic measuring is only possible with global measuring inputs (see Hardware for measuring
inputs (Page 132)(excluding TM15)).
You are not prevented from also using local measuring inputs for cyclic measuring during
configuration. However, this is a pure software solution, and only unique measuring
processes are cyclically collected. The minimum time between two measurements is
therefore much longer than with cyclic measuring with global measuring inputs.
When cyclic measurement is activated with local measuring inputs (command
_enableMeasuringInputCyclic), as of V4.2 Note 40014 is output stating that during cyclic
measuring with local measuring inputs, results may be lost if they are not spaced sufficiently.
Output Cams and Measuring Inputs
Function Manual, 04/2014
5.2 Fundamentals of Measuring Input technology object
First rising edge First falling edge
First falling edge First rising edge
Measuring Input TO - Part III
TM1x; D4xx, D4xx-2 (X122/X132),
CX32, CX32-2, CU320, CU320-2: The
minimum distance of the first edge to be
measured from the previous edge must
be several servo cycles so that the first
edge can be acquired.
D4x5-2 (X142):
No restrictions With hardware support,
the "false" first edge is ignored.
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