Rockwell Automation 1771-KA2 Communication Adapter Module - Manual (Page 55)

Communication Zone Rungs
Chapter 5
5-3
The order of these communication zone rungs is as follows:
1. Header rung
2. Memory access rung(s) (as needed)
3. Command rung(s) (as needed)
4. Delimiter rung
These rungs must always appear in this order at the beginning of the
ladder diagram program. If you are using two KA2 modules, or a
combination of KA2 and -KG modules with the same processor, enter one
immediately after the other.
As a minimum requirement, each station processor must have a header
rung and a delimiter rung. This provides the advantage of an ERROR
CODE storage word, controlled by the module as a diagnostic indicator.
If you are using two communication modules with the same processor,
(possible with 1771-KA2 and 1771-KG series B modules only) you must
program a separate and complete communication zone for each module.
Modules must have different station numbers.
The figures in this chapter show 3-digit addresses above most GET
instructions, but not the 3-digit data value displayed below the GET
symbol. This convention is used for clarity, since, for the most part, only
the 3-digit GET address is significant when entering a program. In
entering communication zone rungs, you needn’t program any data into
GET instructions.
A header rung, as shown in Figure 5.2, indicates the beginning of the
communication zone. For the communication adapter module (cat. no.
1771-KA2), the output position of this rung is always the LATCH 02707
instruction. Header Rungs