The Fc Cnt_Ctl2 Function (Fc 3) - Siemens SIMATIC S7-300 FM 350-1 Manual

Programming the FM 350-1

5.3 The FC CNT_CTL2 function (FC 3)

5.3 The FC CNT_CTL2 function (FC 3)
Functionality
The functionality of FC CNT_CTL2 and FC CNT_CTL1 is basically the same. The differences
between both are explained in the next sections.
Use cases
FC CNT_CTL2 can only be operated in an isochronous OB.
Any call of FC CNT_CTL2 in a non-isochronous OB will generate an operator error 91, and
thus prevent data exchange with FM 350-1.
Principle of operation
FC CNT_CTL2 is in particular suitable for applications for high-speed repetition of a job
request ("Load comparison value", for example) to FM 350-1. Under favorable conditions,
FC CNT_CTL1 lets you initiate a new job at every fifth PROFIBUS DP cycle, whereas FC
CNT_CTL2 supports initiation at every second PROFIBUS DP cycle.
The block is ready to execute a job when the corresponding init bit=0. Completion of a job is
not indicated separately.
Any communication problems, or data errors, or operator errors, can thus not be allocated to
a particular job. In such situations, the block will interrupt job processing, and generate an
operator error 90 which can be acknowledged. You may be able to resume execution of any
queued or interrupted jobs by acknowledging the error by executing parameter OT_ERR_A.
The acknowledgement of an operator error will be accepted if parameter OT_ERR is reset.
Parameter OT_ERR_A should remain set while this action is performed in order to guarantee
acknowledgement. There is no point in initiating further jobs until successful completion of
the acknowledgement.
Note
When operating in isochronous mode, do not use FC CNT_CTL2 to start several
simultaneous value transfers.
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FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01