Shift register

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Short description

The shift register function can be used to read an input value and to shift the bits. The output value corresponds with the configured shift register bit. The shift direction can be changed at a special input.

 

Connection

Description

Input In

The function when started reads this input value.

Input Trg

The SFB is started with a positive edge (0 to 1 transition) at input Trg (Trigger). A 1 to 0 transition is irrelevant.

Input Dir

You define the shift direction of the shift register bits S1...S8 at the Dir input:

Dir = 0: shift up (S1 >> S8)

Dir = 1: shift down (S8 >> S1)

Parameter

Shift register bit that determines the value of output Q.

 Possible settings: S1 ... S8

Retentivity set (on) = the status is retentive in memory.

Output Q

The output value corresponds with the configured shift register bit.

Timing diagram

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Description of the function

The function reads the value of input In with a positive edge (0 to 1 transition) at input Trg (Trigger).

This value is written to shift register bits S1 or S8, depending on the set shift direction:

Q outputs the value of the configured shift register bits.

If retentivity is not enabled, the shift function restarts at S1 or S8 after a power failure.

Note

The special function shift register can be used only once in the circuit program.

 

Overview