Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual - Manual (Page 87)

Introduction to Programming
Chapter 4
4Ć23
WARNING: When the address of an instruction whose data
is to be changed duplicates the address of other instructions
in the user program, the consequences of the change of each
instruction should be thoroughly explored beforehand.
NOTE: When the memory write protect is activated by removing the write
protect jumper, on-line data change will not be allowed for addresses
above 377. If attempted, the industrial terminal will display the error
message MEMORY PROTECT ENABLED.
On-line programming allows changes to be made to the user program
during machine operation when the processor is in the run/program mode
and memory write protect is not active.
WARNING: The task of on-line programming should be
assigned only to an experienced programmer who understands
the nature of Allen-Bradley programmable controllers and the
machinery being controlled. Proposed on-line changes should
be checked and rechecked for accuracy. All possible sequences
of machine operation resulting from the change should be
assessed in advance. Be absolutely certain that the change must
be done on-line and that the change will solve the problem
without introducing additional problems. Notify personnel in
the machine area before changing machine operation on-line.
Maintaining accurate data table assignment sheets and using the data
initialization key described in this section are important steps in
minimizing the chances of error when making on-line programming
changes.
General Rules
Once the memory write protect jumper has been removed, memory write
protect is active, and on-line programming is not allowed. However, data
table values between words 010
8
and 377
8
can be changed using the
on-line data change procedure. In addition, the following rules are always
applicable when programming on-line in run/program mode:
1. As in program mode, output instructions can be changed but cannot
be removed unless the entire rung is removed.
4.4.5
OnĆLine Programming