Siemens SIMATIC ET 200S Operating Instructions Manual page 283

Isochronous mode
Generally applicable information is available in the section "Isochronous mode (Page 267)".
The following particular aspects apply to isochronous mode in the "Pulse width modulation"
operating mode:
● The output always begins without an on-delay, a configured on-delay is ignored.
● The output always begins after the software enable has been issued, a configured
● A change of the time period during runtime is not possible. Corresponding specifications
In isochronous mode, the output sequence is synchronized with the moment T
period is coordinated to the DP cycle. It is possible that your defined time period cannot be
implemented exactly.
The configured value of the time period is adjusted by the 2PULSE to the DP cycle based on
a calculation algorithm. The calculation is performed to minimize the difference between the
specified and calculated time period. In the most unfavorable case, the deviation amounts to
half the DP cycle. The table below shows examples.
DP cycle time T
10 ms
10 ms
10 ms
10 ms
1)
Technological Functions
Operating Instructions, 06/2010, A5E00124867-07
hardware enable is ignored.
via the control interface are ignored.
Specified time period T
1)
DP
5 ms
2 ms
6 ms
16 ms
The calculated time period and the DP cycle time always have an integer ratio.
Calculated time period T
Setpoint
5 ms
2 ms
5 ms
20 ms
2PULSE
5.4 Modes and Functions
. The time
o
1)
Actual
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