Rockwell Automation 1771-KA2 Communication Adapter Module - Manual (Page 91)

Command Initiation, Execution, and
Monitoring
Chapter 7
7-19
communication adapter module. (REMOTE and LOCAL FAULT bits at
other stations indicate the same types of faults that can be detected using a
user-programmed timeout.) A programmed timeout would not be
necessary for each command from a station. Instead, a single command at
each station can be monitored in this manner. Select a command that is
sent regularly for this type of monitoring.
There may be other instances where program monitoring of commands is
useful. In some cases, a user-programmed timeout may be used to
monitor the execution time of critical commands. An application may
require that a critical message, such as a priority command, be sent within
a certain limited amount of time. A programmed TON instruction can be
used for this purpose; here, however, its preset interval will generally be
shorter than the interval entered as the timeout preset for the module.
This chapter dovetailed with chapter 6. It discussed command initiation,
execution, and monitoring and their association with:
START/DONE bit timing
Normal operation
START/DONE bit status
Faulty operation
Control of START bit
ON/OFF input status
Transition of an input device from ON to OFF and OFF to ON
Timed start bits
Diagnostic FAULT rungs
Timeout preset values
Programming a preset code
Optional user-programmed timeouts
Chapter 8 discusses interfacing a KA2 with other modules on a Data
Highway, mastership of the highway and Data Highway computer
commands.
Chapter Summary