Siemens simatic s7-400 FM 450-1, User Manual, Page: 84 / 130

Modes, settings, parameters and commands
8.12 Initiating a process interrupt
Counter module FM 450-1
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Manual, 02/2014, A5E03648739-02
Setting the counter with an external signal
The L_PREPAR input parameter prepares a new load value. You can choose between two
different external signals with which you set a counter to the load value
● Only input 1I2 (2I2)
● Input 1I2 (2I2) and the zero mark of the encoder
You use the zero mark of the encoder if you want to synchronize the counter to a specific
counter status at a specific point in your process. Hence you achieve greater precision in the
count process.
The counter is set independent of the mode.
After setting the counter with an external signal, the STS_SYNC bit is set in the DB. The
STS_SYNC bit is cleared by the RES_SYNC bit.
Note
The synchronization of a counter with the zero mark only makes sense if the gate is open.
When setting a counter with an external signal, if you have only enabled one count direction,
please note the following: When the door closes, only the current count direction is stored
(frozen). Hence it is possible for the counter to be synchronized in the opposite direction to
the enabled count direction.
Hardware interrupt
Setting a counter with an external signal can be used to trigger a hardware interrupt.