Rockwell Automation 1771-KA2 Communication Adapter Module - Manual (Page 60)

Communication Zone Rungs
Chapter 5
5-8
Figure 5.5
Command Rung Format
AAAPX
[ ] (
02707
) [ ]
Command
REFER TO FIGURES
Code
Start
Bit
5.6 AND 5.7
AAA – REMOTE STATION NO.
P – PRIORITY INDICATOR
1 = PRIORITY MESSAGE
0 = NORMAL MESSAGE
X – COMMAND TYPE
0 = PROTECTED WRITE
1 = UNPROTECTED READ
2 = PROTECTED BIT WRITE
3 = UNPROTECTED WRITE
4 = UNPROTECTED BIT WRITE
After the command code, the command rung then lists the memory areas
affected by the command. The format of this area varies, based upon the
type of memory area controlled by the command.
The length of the communication zone in PLC-2 family PCs is limited by
the memory available inside the communication module. Very few
applications approach this limit, but if you program too many command
rungs, the value 26 will appear in the error code word when you place the
processor in RUN or RUN/PROGRAM mode.
Each command rung ends with an OUTPUT ENERGIZE 02707 element.
This instruction is used solely for the purpose of fitting the command rung
into the proper display format. The output instruction of the command
rung has no significance in program logic.
Examine START Bit
Each command rung has a unique START bit in a memory word selected
by the programmer. (Refer to section titled “START/DONE Word,”
chapter 6). The START bits are examined by the communication adapter
module. When a START bit is on, the communication adapter module
carries out the programmed command.