Siemens SIMATIC S7-300 FM 350-1, Manual

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Operating Modes, parameters and commands
7.3 Count modes
FM 350-1 Counter module
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Manual, 05/2011, A5E03648639-01
Main Count Direction
When you set a main count direction (up or down), you can limit the maximum count range
to a smaller range by setting the high count limit. The set count range is then between 0 and
the set high counter limit. This can be used to create incrementing or decrementing counting
applications, for example. The set main count direction has no effect on the direction
evaluation when the count pulses are detected.
Starting Counts According to Parameterization
Table 7- 3 Start values
Value Main count direction Start value
Load value None
Up
Down 0
0
Parameterized high count limit
Count value None
Up
Down 0
0
Parameterized high count limit
Comparison value 1 and 2 None
Up
Down 0
0
Parameterized high count limit
Latch value None
Up
Down 0
0
Parameterized high count limit
Isochronous Mode
In isochronous mode, the FM 350-1 accepts control bits and control values from the control
interface in each PROFIBUS DP cycle and returns its response to them within the same
cycle.
In each cycle, the FM 350-1 sends the counter state or latch value that was valid at the time
T
i
and the status bits that were valid at the time T
i
.
Thus, a counter level that is affected by hardware input signals can only be transferred in the
same cycle if the input signal occurs before the time T
i
.