Siemens et 200sp - Isochronous Mode

Configuring/address space
4.6 PWM with DC motor motor
Technology Module TM Pulse 2x24V (6ES7138‑6DB00‑0BB1)
122 Manual, 05/2019, A5E35061186-AB
4.6.6 Isochronous mode
The technology module supports the "Isochronous mode" system function. In isochronous
mode, the output sequence starts at time T
o
after the SW_ENABLE control bit has been set.
The period duration is also adapted to the application cycle (T
APP
) and synchronized with it.
The synchronization is especially advantageous for setting up control loops.
The module adjusts the assigned value of the period duration in such a way that an integer
ratio results. In the most unfavorable case, the difference amounts to half the application
cycle.
Examples:
Application cycle
T
APP
Assigned period duration
T
Setpoint
Actual period durationT
Actual
T
APP
:T
Actual
10 ms
(10000 μs)
1800 μs
1666 μs
6:1
2000 μs
2000 μs
5:1
3000 μs
3333 μs
3:1
5000 μs 5000 μs 2:1
6000 μs
5000 μs
2:1
12000 μs
10000 μs
1:1
16000 μs
20000 μs
1:2
The figure below shows an example of a 1:1 ratio of application cycle to period duration with
a duty cycle of 50%.
The figure below shows an example of a 3:1 ratio of application cycle to period duration with
a duty cycle of 50%.