Rockwell Automation 9323-S5500D A.I. SERIES MICROLOGIX 1000 AND PLC-500 SOFTW - Manual (Page 449)

MicroLogix 1000 and PLC-500 A.I. Series Software Reference
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I/O Forcing
The Force function allows you to override the actual status of external input circuits by
forcing external input data file bits On or Off. You can also override the processor
logic and status of output data file bits by forcing output circuits On or Off.
You can install and then enable or disable forces while either:
•
monitoring your file offline; or
•
monitoring your file online in any processor mode.
!
All force functions can result in sudden machine movement, possibly causing death,
personal injury, or damage to equipment. Investigate the effects on machine
operation before forcing external input data file bits or external output circuits. USE
EXTREME CAUTION WHEN FORCING I/O!
!
MicroLogix 1000 users: Forces are always enabled in MicroLogix 1000 controllers.
When forcing I/O points, the forces take effect as soon as they are placed!
!
MicroLogix 1000 users: The controller will cause a major fault if you force an output
bit ON that does not exist as an actual output point on the controller. See the
information on status bit S:0/8 in Appendix A - Programming Reference for Packaged
Controllers in the Instruction Set Reference for information on changing this
response.
Forces to both inputs and outputs are stored in an area of SLC 500 memory called the
force table. The force table can be thought of as a data filter between the actual I/O and
the data table image of the I/O.