Rockwell Automation 1747-SCNR ControlNet Scanner Module Reference Manual - Manual (Page 77)

1 Publication 1747-RM623D-EN-P - June 2006
Appendix D
Example of Reset Bit Management
What This Appendix Contains This appendix contains an example of how you can use the
ladder program to reset a 1747-SCNR module located in the SLC
500 rack.
What We Assume We assume that you are familiar with ladder programming.Reset
bit management is illustrated in the following example. The
steps in the procedure correspond to the steps in the illustration
following.
Example Reset bit management is illustrated in the following example.
The steps in the procedure correspond to the steps in the
illustration.
1 . In this example, we reset the scanner when it is faulted.
When the 1747-SCNR sets its fault bit, the scanner slot
(slot 3) is disabled and the Output Command word Reset
bit is set (O:3.0/8).
2. When the slot is disabled, a timer is started and four
seconds later the scanner is enabled.
During these four seconds, you must avoid any access to
the scanner in reset. This is why the rung with the TND
instruction must be executed first.
IMPORTANT
If you do not disable the slot while the scanner is
resetting, the SLC module faults with the error code
nn57h (speciality, I/O Module in slot nn has not
responded to a lock shared memory command in the
requested time limit) where nn is the slot number of
the scanner. This is why the reset bit change is not
taken into account until the slot is disabled.