¨no program¨ when an event task is started by SYSTEM_FLAGS

Which products are affected?
EVS93xx-EI (Servo PLC V6.x)
EVS93xx-ET (Servo PLC V6.x with technology function)
EPL-10200 (Drive PLC V6.x)
ECS axis module: ECSxx operating software V6.x

What happens?
If a DDS project has been downloaded into the PLC target system and started afterwards the PLC target system indicates a PEr trip (C0161 = 74). The PLC project is not started. After mains connection the PLC target system indicates the error message 'no program' (C0161 = 230).

When does the problem occur?
The response described before may occur if a system variable of the SYSTEM_FLAGS system block is used to start an event-controlled task (EVENT task), e. g. SYSTEM_bClock1Hz.

Possible diagnostics?
Check on the Task Monitor (DDS: tab Resources) under column Event if the system variable of the SYSTEM_FLAGS system block is used to call up a task.

Short-term measures/recommendations?
Do not use system variables of the SYSTEM_FLAGS system block to start an event-controlled task.
Instead of an event-controlled task which is started by a SYSTEM_bClockxHz system variable it is also possible to use a time-controlled task (INTERVAL task).
Alternative: Copy the system variable selected to a global variable in a time-controlled task and use this global variable to start the event-controlled task.

Evaluation:
In practice an event-controlled task is usually not started by means of a system variable of the SYSTEM_FLAGS system block. The PLC is stopped by a PEr trip or 'no program' message immediately after the download of the PLC project.

URL for linking this AKB article: https://www.lenze.com/en-de/go/akb/200605991/1/