Siemens SIMATIC ET 200SP Manual page 29

For more details about SLOT parameter handling, see "Slot parameter handling (control
interface) (Page 113)".
Isochronous mode
General information is available in the "Function: Isochronous mode (Page 86)" topic.
In isochronous mode, the output sequence is synchronized with the moment T
duration is coordinated to the application cycle (the synchronous cycle, a multiple of the
PROFINET cycle). It is possible that your assigned period duration cannot be implemented
exactly. The configured value of the period duration is adjusted by the TM Pulse 2x24V to
the application cycle based on a calculation algorithm. The calculation is performed to
minimize the difference between the assigned and calculated period duration. In the most
unfavorable case, the deviation amounts to half the application cycle. The table below shows
examples.
Application cycle Assigned period duration
T T
1
CAC Setpoint
10 ms (10000 μs)
10 ms (10000 μs)
10 ms (10000 μs)
10 ms (10000 μs)
10 ms (10000 μs)
10 ms (10000 μs)
10 ms (10000 μs)
10 ms (10000 μs)
The calculated actual period duration and the application cycle time always have an integer ratio (1:1, 1:2, 1:3, ..., 2:1,
1
3:1, ... ) rounded down to the next possible value.
The timing between the digital output and the application cycle is shown below. The DQ duty
cycle (On/Off) ratio is shown in the examples at 50%.
● Example 1: The period duration 10000 μs is equal to the application cycle time 10 ms
(10000 μs).
Technology module TM Pulse 2x24V (6ES7138‑6DB00‑0BB1)
Manual, 09/2015, A5E35061186-AA
T \ T
CAC
5000 μs 2:1
2000 μs 5:1
3000 μs 3:1
1800 μs 6:1
6000 μs 2:1
12000 μs 1:1
16000 μs 1:2
26000 μs 1:3
3.3 Pulse width modulation (PWM) mode
Calculated actual period duration
T
1
Actual Actual
5000 μs
2000 μs
3333 μs Next possible value is used as actual value
1666 μs Next possible value is used as actual value
5000 μs Next possible value is used as actual value
10000 μs Next possible value is used as actual value
20000 μs Next possible value is used as actual value
30000 μs Next possible value is used as actual value
Modes and Functions
. The period
O
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