Test stop/forced checking procedure of the TM54F

Owned by Gary Foster
Dec 26, 2023
3 min read

S120 support link

Testing fail-safe inputs and outputs

Fail-safe I/O must be tested at defined intervals in order to validate their fail-safety (test stop or forced checking procedure). For this purpose, TM54F has a function block, which executes this forced checking procedure in the following cases:

  • When selected via a BICO source

  • Automatically, each time the power supply voltage is switched on (POWER ON)

To monitor the time until the next required test, a timer (p10003) is started after every error-free test stop/forced checking procedure. The message A35014 "TM54F test stop necessary" is set on expiration of the monitored time and each time the Control Unit is switched on.

The fail-safe digital inputs can be selected for the test stop/forced checking procedure. 3 modes can be selected to test the outputs (see following sections).

When the appropriate safety devices are implemented (e.g. protective doors), it can be assumed that running machinery will not pose any risk to personnel. For this reason, an alarm is only output to inform the user that a forced checking procedure run is due and to request that this be carried out at the next available opportunity.

Examples of when to carry out forced checking procedure:

  • When the drives are at a standstill after the system has been switched on

  • Before opening the protective door

  • At defined intervals (e.g. every 8 hours)

  • In the automatic mode, time and event-dependent

  • Automatically, each time the power supply voltage is switched on (POWER ON)

Execution

When parameterizing, proceed as follows:

  1. Derive the appropriate mode from the circuits used in your application (see diagrams in the following sections).

  2. Set the mode which is to be used via parameter p10047.

  3. Use parameter p10046 to define which digital outputs (F‑DO 0 to F‑DO 3) are to be tested. Note the following:

    Digital outputs, which are not tested, are switched off during the test stop/forced checking procedure.

  4. Use parameter p10041 to define which fail-safe digital inputs are to be checked during the test.

    Inputs which do not have L1+ and L2+ power supplies may not be selected for the test.

    It is only possible to test the sensors connected to the F-DIs, if these are supplied from L1+ or L2+. If F-DOs of upstream processing devices are connected, then the test stop/forced checking procedure cannot be used for this input.

  5. Use parameter p10001 to set the time within which the digital output signals to the corresponding digital inputs DI 20 ... DI 23 or DIAG inputs must be recognized. Select this time depending on the maximum response time of the external F‑DO circuit.

  6. Use parameter p10003 to set the interval within which a test stop/forced checking procedure should be carried out. After this time interval has expired, you will be notified via message A35014 that a test stop/forced checking procedure must be performed for the TM54F.

  7. Set the signal source which triggers the start using parameter p10007. This can be, for example, a control signal or switch via a BICO switchable signal.

    Alternatively, the test stop/forced checking procedure can be automatically performed each time that the power supply voltage is switched on (POWER ON) (p9507.6 = 1).

During execution, message A35012 (TM54F: Test stop active) is displayed. The F-DI values are frozen for the duration of the test stop/forced checking procedure. The messages A35014 and A35012 only disappear again after the execution. If an error is found during the test, fault F35013 is output. Using the test sequence specified for each mode, you can see which error has occurred from the fault value of the test step.

Caution

The F-DO feedback signal may only be used for the test stop/forced checking procedure

Please note that F-DO may only be used for the feedback signal for the test stop/forced checking procedure, and not for other purposes. The sequence could otherwise initiate undesirable drive responses.

 

Test stop / forced checking procedure: Duration

You can calculate the duration using this formula:

F-DOs which are not registered for evaluation by means of p10046 are set to "0" for the duration of the test ("fail-safe values").

The maximum time period for the test is: TTest stop = TFDIs + TFDOs

  • Test of the FDIs: TFDIs = 3 × p10000 + 3 × X ms

    (X = 20 ms or p10000 or p10017 - the greatest time value of the 3 values determines the waiting time X)

  • Test of the FDOs: TFDOs = 8 × p10000 + 6 × Y ms

    (Y = p10001 or p10000 or p10017 - the greatest time value of the 3 values determines the waiting time Y)