Siemens SIMATIC S5-100U, System Manual

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S5-100U Function Modules
Performance during Overflow
If the enabled counter exceeds the counter range limit 65,535 the following occurs:
• Bit 3 (overflow) in the diagnostic byte is set to “1”.
• The outputs and diagnostic bits for “setpoint reached” are disabled, but they remain unchanged.
The counting function continues. Thus the actual value is constantly updated.
You can continue to read all data from the module in the STEP 5 program:
• The updated count
• The status of the outputs at the time of the overflow (This status remains unchanged until the
overflow bit is reset.)
• The set overflow bit
After an overflow, the counter can be reset by one of the following actions:
• A positive edge at the enable input
• An overall reset of the programmable controller (STOP to RUN mode)
Note
After a cold restart of the programmable controller, the outputs are disabled. These
outputs can be enabled via a positive edge to the enable input.
15.6.4 Functional Description of the Position Decoder
In the operation mode “position decoder” the module works as an up/down-counter and counts the
pulses of the connected position encoder. Because of the phase offset of the two decoder signals
A and B, the counter determines the counting direction. If the counter reaches a preselected set-
point, the respective output is then turned on.
Settings
Set the following items on the operating mode switch:
• “Position decoding” (PD) function
• The desired position resolution (single, double, or quadruple)
• The signal level of the counting pulses (5 V or 24 V)
EWA 4NEB 812 6120-02b
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