Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 187)

Application Example 2, Periodic Block
Transfer
Appendix C
CĆ3
The circumstances in which the load/enter sequence is program initiated
are:
1. Processor Power-Up: On the first scan of user program, program
logic will initiate a load/enter sequence. This is true for powering up
the PC processor in the run mode and when PC processor operation
is changed from program or test mode to run mode.
2. Alarm Condition at Module: Should a condition occur at the module
which causes any of the diagnostic bits in the status monitor byte to
be set, the user program will automatically begin to execute
continuous load/enter sequences until the alarm condition is
corrected. This will allow an operator to observe the source of error
in diagnostic word W60 and to manually enter commands to clear
the fault. Once the alarm condition is corrected, the program will
stop executing load/enter sequences and return to its original
operating state.
If the following limiting functions are not used, enter the maximum value
from the table to prevent the processor from initiating nuisance load/enter
sequences.
Limit Word Max Value
EMN W21(W41) Ć4095
EMP W22(42) +4095
V
I
MAX W26(W46) 9999
V
D
MAX W27(W47) 9999
V
D
MIN W28(W48) 0000
VMAX W29(W49) 4095
The circumstances in which the load/enter sequence is initiated manually
are:
1. Pushbutton Initiated: A load/enter sequence can be executed
manually at any time. An example would be changing the loop gain
constants. The program examines the contacts of a pushbutton
switch. When the contacts close, one load/enter sequence will be
executed. To execute another sequence, the contract must open and
close again.