Rockwell Automation 1771-KA2 Communication Adapter Module - Manual (Page 53)

Chapter
5
5-1
Communication Zone Rungs
At the beginning of the ladder-diagram program, you enter a special set of
rungs that dictate communication adapter module activity. The KA2 scans
this set of rungs at power-up for operating information.
WARNING: Do not make on-line edits of the communication
zone. Since the module scans the communication zone only
when it powers up or when the processor changes state (from
program to run), the changes will not affect module operation
until you cycle power to the 1771-KA2 module or change the
operating mode of the processor. Attempting such edits may
cause unexpected communication on the Data Highway.
Communication zone rungs use the standard controller instruction set.
However, the meaning of these instructions and addresses differs
significantly from their meaning in standard ladder-diagram
programming. For this reason, each programmed element in a
communication zone rung must be understood as it is described in this
chapter, not as it would normally be understood in a ladder- diagram logic
context.
In several instances, the 3- or 5-digit number entered above the
communication zone rung element has no relation to an actual data table
address. This chapter specifically identifies this type of number as either
a station number or code. Where one of these designations is given, the
actual data table bit or word at that address is not affected by KA2 module
operation and may be used in the balance of the user program.
For the purpose of this description, the reference point is termed the local
station. All other stations are then considered remote stations. These rungs
are entered at the local station so that it can send commands to, or receive
commands from a remote station.
Obviously, this reference point is not fixed. Each station - as it is being
programmed - is considered the local station at that time.
General