Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 66)

Programming
Chapter 3
3Ć23
value VMIN in word W28 (W48) and the maximum value VMAX in
word W29 (W49). Limiting is not performed on the SET OUT value
in word W05 (W12).
W19 (W39) B15, B14, B13. Soft Fault Mode Selection. These bits
select the PID module’s response for the loop when communication
with the PC processor is broken. The PID module’s microprocessor
continues to operate and is firmware programmed to respond to the
fault. The PID module’s STAND-ALONE yellow LED indicator
flashes when the module is in the soft fault mode.
NOTE: In order for the PID module to operate in the soft fault
mode, the last state witch (switch 1) in the switch group assembly on
the I/O chassis backplane must be set to the off position. As such,
output of all other modules in the chassis will be de-energized when
a major fault is detected by the PC processor.
NOTE: When the PID module enters the soft fault mode, it does not
generate a manual request to relinquish control to the auto/manual
station. However, if the PID module detects a hardware failure when
in soft fault mode it will generate a manual request.
The soft fault operating modes are listed in Table 3.E.