Siemens LOGO! Manual page 192

LOGO! functions
4.4 Special functions list - SF
Functional description
The function reads the value at input In with a positive edge (0 to 1 transition) at input Trg
(Trigger).
This value is applied to shift register bit S1 or S8, depending on the shifting direction:
● Shift up: The value at input In is set at S1; the previous value at S1 is shifted to S2; the
previous value at S2 is shifted to S3 etc.
● Shift down: The value at input In is set at S8; the previous value at S8 is shifted to S7; the
previous value at S7 is shifted to S6 etc.
Output Q returns the value of the configured shift register bit.
If retentivity is disabled, the shift function restarts at S1 or S8 after a power failure. When
enabled, retentivity always applies to all shift register bits.
Note
The special function shift register can be used only once in the circuit program.
Timing diagram
192
Manual, 10/2017, A5E01248535-AA
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