Chapter 10 Maintenance
XBC E-Type Main Unit 10-28 Ver. 1
10.9.2 Input/Output Forcing Description and Considerations
Input and Output forcing allows for simulating a process with the PLC during program development. Forcing is
also used when a field device is not available or defective. Forcing in only available for P Area memory (physical
I/O). Any combination of I/O can be assigned for forcing. During forcing, the Input and Output image table is
updated with the Forced data. While the PLC logic still processes the PLC program, the forced information
overrides the actual I/O status.
Cautions and considerations when using I/O Forcing
1. After setting a force condition in the module force table, the Apply button must be clicked to update the
forced conditions.
2. Forced I/O can be selected and modified though a physical device is not attached to the system.
3. A forced I/O state will remain after a PLC power cycle or a Reset from the Online menu.
4. A forced I/O state will remain in the forced condition in the STOP Mode of the PLC.
5. To removed forced I/O it must be Deselected and click Apply. It is recommended to perform a Delete
All to be sure all forces are removed.
Forcing behavior during an error condition.
1. When an error occurs, the PLC I/O will operate based on the parameter settings for the I/O; “Emergency
output” and “Keep output when an Error Occurs.” If “Emergency Output” (Project Tree > Parameter > I/O
Parameter > Emergency Output) is to Clear AND “Keep Output When an Error Occurs” (Project Tree >
Parameter > Basic Parameter > Basic Operation Settings > Output control Settings) is checked, the
following operation can be expected: When an error occurs, Output is cleared.
However, if “Emergency Output” is set to Hold AND “Keep Output When an Error Occurs” is checked,
Output is held when an error occurs.
2. If “Keep Output when an Error Occurs” is Unchecked, the Output will be OFF when an error occurs.
CAUTION: FORCING I/O CAN HAVE VERY UNPREDICTABLE RESULTS IF ONE IS NOT VERY FAMILIAR
WITH THE EQUIPMENT OPERATION. USE EXTREME CAUTION WHEN USING THE FORCE I/O
FUNCTION. FORCE I/O IS A BENEFICIAL TOOL WHEN USED CORRECTLY AND WITH CARE.
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