Rockwell Automation 1771-KA2 Communication Adapter Module - Manual (Page 39)

Commands
Chapter 4
4-3
Terminology: Remote/Local Station
In this and later chapters, we use the terms “remote station” or “local
station.” The local station is the point of reference. When describing the
commands, for instance, the local station is the one sending the command.
A remote station is any station that receives a command from the local
station.
Figure 4.1 illustrates this terminology.
Each 1771-KA2 module command has a prefix, either “protected” or
“unprotected.” This prefix denotes memory access of the command. The
distinction between these command types is:
Protected commands can access (write into) only specified data table
areas. The program in the receiving station processor controls these areas.
In that program, a memory access rung determines which data table areas
will accept protected write or protected bit write commands. (Rungs are
described in chapter 5.) The receiving station ignores protected
commands that are not defined by the memory access rung.
Unprotected commands require no memory access rung, and they can
read or write into any addressable data table word in the receiving station
processor.
The primary distinction between these commands is program restriction
of memory access. Switch selections can also be made on the module for
write protection, to enable/disable execution of many of these commands.
(Chapter 3 gives switch selections.)
Figure 4.2 summarizes the distinction between protected and unprotected
commands.
Protected/Unprotected