Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 151)

Special Programming Techniques
Chapter 11
11Ć4
The data stored at the instruction address is divided into two sections: status bits
(bits 14-17) and BCD values (bits 00-13). During program execution, these bits
are constantly changing to reflect current states and values of program
instructions. Therefore, when programming on-line, a decision must be made
whether to use the current data or enter new data.
Use the [DATA INIT] key when adding an instruction containing new data. Do
not use it when adding an instruction that will use the data at a pre-assigned
address.
The [DATA INIT] key performs two functions in the on-line programming
mode:
It allows entry of BCD data values (stored at the instruction address).
It assures that the status bits are cleared to 0000.
Use the [DATA INIT] key when programming a data instruction whose address
is not currently being used in the program. If the [DATA INIT] key were not
used, data at the new address (possibly remaining from previous programming)
may interfere with proper machine operation when you insert the new
instruction into the program.
WARNING: When the address of a new instruction duplicates
the address of other instructions in the program, the [DATA
INIT] key should not be used without first assessing the
consequences. Pressing the [DATA INIT] key will zero out the
status bits stored at the existing instruction address. This may
interfere with desired machine operation. Damage to equipment
and/or injury to personnel could result.
To look for a specific instruction, press [SEARCH] (key sequence of the
instruction). To look for a specific address, press [SEARCH] (key sequence of
the address). This will help you to determine addresses currently used in your
program.
To locate all addresses (excluding those associated with examine on and
examine off instructions and those contained within files) press [SEARCH][8]
(key sequence of the address). The address entered is the word address. For the
output energize, latch and unlatch instructions, the industrial terminal will locate
all of the bit addresses associated with the word address.
The message “SEARCH FOR” and the entered key sequences will be displayed
at the bottom of the screen. The message “EXECUTING SEARCH” will
appear temporarily. The industrial terminal will begin to search for the address
and/or instruction from the cursor’s position. It will look past the temporary
end and subroutine area boundaries to the END statement. Then it will continue
searching from the beginning of the program to the point where the search
began.