Siemens SIMATIC ET 200S Operating Instructions Manual page 201

If you close the SW gate, it only interrupts counting; this means that when you open the SW
gate again, counting is continued. The digital input DI remains active even when the SW
gate is closed.
Counting is also latched and triggered in isochrone mode with each edge on the digital input.
The count that was valid at the time of the last edge before T
interface.
The Latch function
In order to use this function, the Function DI parameter "Latch on Positive Edge" must be
selected for the digital input.
Figure 3-39
Count and latch value are preset with their RESET states (see corresponding table).
The counting function is started when the SW gate is opened. The 1Count5V/500kHz begins
at the load value.
The latch value is always the exact count at the time of the positive edge on the digital input
DI.
The stored count rather than the current count is indicated in the feedback interface. The
STS_DI bit indicates the level of the latch signal.
Direct loading of the counter does not cause the indicated stored count to be changed.
In isochrone mode, the count that was latched at the time of the last positive edge before T
is displayed in the feedback interface.
When you close the SW gate, the effect is either canceling or interrupting, depending on the
parameter assignment. The digital input DI remains active even when the SW gate is closed.
Technological Functions
Operating Instructions, 02/2007, A5E00124867-05
Latch with a Load Value of 0
1Count5V/500kHz
3.8 Position feedback
is displayed in the feedback
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