Which products are affected? - EPL-10200 (Drive PLC, operating system versions 2.0, 2.1, 2.2)
- EVS93xx-EI (9300 Servo PLC, operating system versions 2.0, 2.1, 2.2)
- EVS93xx-xT (9300 Servo PLC, operating system versions 2.0, 2.1, 2.2)
What happens? With function block L_ParWrite it is possible that sometimes all tasks are not processed for the duration of the system task (typically approx. 10 … 20 ms). Especially with positioning applications, controller characteristic parameters (e.g. speed setpoint) will not be calculated if a task is inhibited.
When does the problem occur? The behaviour described above can occur in every application with L_ParWrite. Especially with positioning applications, a data set consisting of position, acceleration, speed and delay is used to calculate a positioning profile which is to be moved by the drive. Tasks calculate and scan the typical controller characteristic parameters (following error, actual speed, etc). If the task is inhibited, these controller characteristic parameters will not be calculated further. A following error will be added and suddenly reduced again after the inhibit.
Possible diagnostics? None
Short-term measures? For applications with speed processing:
We recommend using function block L_ParWrite only if the speed setpoint has not changed. This is possible at constant speed or standstill. As a result, it can be ensured that a task is not inhibited during a positioning profile.
General:
If L_ParWrite is carried out, it must be ensured that code C2102 is set at 2 and code C2100 is set at 26 ms. Moreover, please consider the maximum runtime of the PLC_PRG and system task on the task monitor of the Drive-Developer-Studio.
Recommended setting:
Observation on the task monitor:
- PLC_PRG runtime < 24 ms (runtime on task monitor, 2 ms reserve to the recommended setting)
- System task runtime < 24 ms (runtime on task monitor, 2 ms reserve to the recommended setting)
The following drawing shows the results of a task inhibit (the time Tinhibit depends on the setting of the task change between system task and cyclic task; Setting: C2102 = 2 (task change after cycle end of PLC_PRG and system task) and C2100 = 26 ms (time slot of cyclic task)):
