Forcing; Forcing Outputs "Force; Forcing Variables "Force Var - Siemens SIMATIC S5 Manual

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S5-115F Manual
4.2

Forcing

You can use the Forcing functions to influence specific binary and digital operands. A distinction is
made between Forcing Outputs (FORCE) and Forcing Variables (FORCE VAR), depending on
whether the process image or program scanning is influenced. Both functions are possible in the
S5-115F only in Test mode.
4.2.1

Forcing Outputs "FORCE"

You can set ouputs to a specific signal state directly without using the control program. Use this
direct method to check the wiring and functioning of output modules. This procedure does not
change the process image but it does cancel the output disable state.
Note
For the "FORCE" test function, the PLC must be in "STOP" mode.
4.2.2

Forcing Variables "FORCE VAR"

With the "FORCE VAR" test function, the process image of binary and digital operands is modified
regardless of the PLC mode.
The following variables can be modified: I, Q, F, T, C, and D.
Program scanning with the modified process variables is executed in the "RUN" mode. However,
the variables can be modified again in the remaining program run, without a checkback signal.
Process variables are forced asynchronously to the program run.
Special characteristics include the following:
Modify the variables I, Q, and F only by bytes or by words in the process image.
For the variables T and C in the KM and KH format, proceed as follows:
- Enter a "Y" in the SYS. OPS. input field in the Defaults menu (only in the case of the PG 675).
- Pay particular attention to forcing of edge trigger flags.
An incorrect format or operand input interrupts the signal status display. The system outputs
the message "NO FORCE POSSIBLE".
EWA 4NEB 811 6149-02
Program Test
4-3

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