Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 149)

Special Programming Techniques
Chapter 11
11Ć2
NOTE: If a particular function or instruction directory or an item in a directory
is not available with the Mini-PLC-2/16 processor, the industrial terminal will
display a “FUNCTION NOT AVAILABLE WITH THIS PROCESSOR”
message if the key sequence is pressed.
You can change (while the processor is in the run/program mode) the lower 12
bits of a word or word instruction. this excludes arithmetic and put instructions,
or certain data of a block instruction. To do this, position the cursor on the
appropriate instruction and press [SEARCH][5][1]. The message “ON-LINE
DATA CHANGE, ENTER DIGITS FOR; (required Information)” will be
displayed near the bottom of the screen. The new digits will be displayed in a
command buffer as they are entered. Use the [
→
] and [
←
] cursor control keys
as needed. After the new data is displayed, press [INSERT]to enter the data
into memory.
To terminate this function, press [CANCEL COMMAND].
WARNING: When the address of an instruction whose data is to
be changed duplicates the address of other instructions in user
program, the consequences of the change for each instruction
should be thoroughly explored beforehand. This is to guard
against unexpected machine operation which could result in
damage to equipment and/or injury to personnel.
NOTE: When the memory write protect is activated by the EPROM back-up
memory, on-line data change will not be allowed for addresses above 177. If
attempted, the industrial terminal will display the error message: MEMORY
PROTECT ENABLED.
On-line programming allows you to make changes 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; and 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.
To minimize the chances of error, maintain accurate data table assignments
sheets and use the data initialization key described later in this section.
OnĆLine Data Change
OnĆline Programming