Siemens LOGO!, Manual

Page: 150 / 534

LOGO! functions
4.3 Special Functions
LOGO!
150
Manual, 04/2011, A5E03556174-01
4.3 Special Functions
Because of their different input designation, you can see right away that there is a difference
between the special functions and basic functions. Special functions (SFs) contain timer
functions, retentive functions and various parameter assignment options, which allow you to
adapt the circuit program to suit your own requirements.
This section provides you with a brief overview of input designations and with some
particular background information on SFs (Page 156).
4.3.1 Designation of the inputs
Logical inputs
Here, you will find the description of the connectors you can use to create a logical link to
other blocks or to the inputs of the LOGO! unit.
●
S (Set):
A signal at input S sets the output to logical "1".
● R (Reset):
The reset input R takes priority over all other inputs and resets the outputs.
● Trg (Trigger):
This input is used to trigger the start of a function.
● Cnt (Count):
This input is used for counting pulses.
● Fre (Frequency):
Frequency signals to be evaluated are applied to this input.
● Dir (Direction):
This input determines the direction, + or -.
● En (Enable):
This input enables a block function. When this input is "0", other signals to the block will
be ignored.
● Inv (Invert):
A signal at this input inverts the output signal of the block.
● Ral (Reset all):
All internal values are reset.
The following connector is available only in the device series 0BA7:
●
Lap (for the stopwatch function)
A signal at this input pauses the stopwatch.
Note
Unused logical inputs of special functions default to logical "0".