Rockwell Automation 1772-LP3 PLC - 2/30 Programmable Controller Programming and Operations Manual User Manual
Page 88
Introduction to Programming
Chapter 4
4Ć24
2.
Block Transfer Read and Write instructions, Jump, Jump to
Subroutine, MCR, ZCL and Temp End instructions cannot be
inserted.
3.
The Label instruction cannot be inserted or removed directly, nor can
the rung containing it be removed. However, the Label instruction
can be changed to another instruction.
CAUTION: When editing out a Label instruction, all Jump and
Jump to Subroutine instructions with the same label number
must be removed. If not, a run-time error will occur when the
processor executes the Jump to Subroutine instruction.
Data Initialization Key
When programming many kinds of instructions, such as the Get, Les, Equ,
Timers and Counters, Files, Sequencers and Shift Registers, two types
of information must be entered. They are the instruction address and
operating parameters. The data stored at the instruction address is divided
into two sections: status (bits 14-17) and BCD value (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 by the user whether to use the current
data or enter new data. The [DATA INIT] key is used for entering new
data.
The [DATA INIT] key performs two functions in on-line programming
mode:
It allows entry of BCD data values (stored at the instruction address)
Clears the status bits to 0000 (except for FIFO instructions which
initially have an empty stack, and hence, bit 14 must be one)
The [DATA INIT] key should be used when programming an instruction
whose address is not currently being used in the program. In this case,
using the [DATA INIT] key allows:
BCD values to be entered
Assures the status bits are set to zero
If the [DATA INIT] key were not used, data at the address (possibly
remaining from previous programming) may interfere with proper machine
operation when the new instruction is inserted into the program.