Rockwell Automation 1769-IR6 Compact I/O 1769-IR6 RTD/Resistance Input Module - Manual (Page 17)

Rockwell Automation Publication 1769-UM005B-EN-P - March 2012 17
Overview Chapter 1
General Diagnostic Features
A single diagnostic indicator helps you identify the source of problems that
may occur during powerup or during normal channel operation. The indicator
shows both status and power. See Chapter 5,
Diagnostics and Troubleshooting , for
details on power-up and channel diagnostics.
System Overview The modules communicate to the local controller or communication adapter
through the 1769 bus interface. The modules also receive 5 and 24V DC power
through the bus interface.
System Operation
At powerup, the module performs a check of its internal circuits, memory, and
basic functions. During this time, the module status indicator remains off. If
no faults are found during power-up diagnostics, the module status indicator is
turned on.
After power-up checks are complete, the module waits for valid channel
configuration data. If an invalid configuration is detected, the module
generates a configuration error. Once a channel is properly configured and
enabled, the module continuously converts the RTD or resistance input to a
value within the range selected for that channel.
Each time the module reads an input channel, it tests the data for a fault (over-
or under-range, short-circuit, or open-circuit condition). If it detects a fault,
the module sets a unique bit in the channel status word. See Input Data File on
page 47.
Using the module image table, the controller reads the two’s compliment
binary converted input data from the module. This typically occurs at the end
of the program scan or when commanded by the control program. If the
controller and the module determine that the data transfer has been made
without error, the data is used in the control program.