IEC function block FB_CheckSTOStatus
The function block checks the 4 possible combinations of the two STO inputs STO_1+, STO_2+ and the resulting internal signal STO_Output_Status.
STO_1+ | STO_2+ | STO_Output_Status |
|---|---|---|
0 | 0 | 1 |
0 | 1 | 1 |
1 | 0 | 1 |
1 | 1 | 0 |
The axis with the STO signal to be checked is transferred to the Axis variable. The check is started with xEnable. The tMaxTimeForSTOCheck input specifies the time in which the STO check must be performed. The "STO_1+", "STO_2+" and "STO_Output_Status" signals are read within the function block using the FB_Read_STO-and_OutputStatus command via CoE.
The STO inputs STO_1+ and STO_2+ are connected by a safety-technology component, usually a safety controller. The order of the STO combinations to be tested is not relevant. The function block stores the successful combinations internally. It is important that all combinations are run through within the time specified at the tMaxTimeForSTOCheck input in order for the STO check to be successful.
If the STO check is successful, the xSuccess output switches; in the event of an error the xError output switches.
Possible causes of errors are, for example, STO combinations that are not permitted or exceeding the specified time for the check. An error is output at the strMessage output in plain text.
