Rockwell Automation 1746-NI8 SLC 500 Analog Input Modules User Manual - Manual (Page 13)

1–3 Overview
Publication 1746Ć6.8 - April 1997
General Diagnostic Features
The 1746-NI8 module contains diagnostic features that can help you
identify the source of problems that may occur during power-up or
during normal channel operation. These power-up and channel
diagnostics are explained in chapter 7, Module Diagnostics and
Troubleshooting.
The module communicates to the SLC 500 processor through the
parallel backplane interface and receives power from the SLC 500
power supply through the backplane. The +5V dc backplane supply
powers the SLC circuitry, and the +24V dc backplane supply powers
the module analog circuitry. No external power supply is required.
You may install as many 1746-NI8 analog modules in your system as
the power supply can support.
Each channel on the module can receive input signals from voltage
or current analog input devices. You configure each channel
individually to accept either a voltage or current input signal.
System Operation
At power-up, the module performs a check of its internal circuits,
memory, and basic functions. During this time the module status
LED remains off. If no faults are found during the power-up
diagnostics, the module status LED is turned on.
After power-up checks are complete, the module waits for valid
channel configuration data from your SLC ladder logic program
(channel status LEDs off). After configuration data is written to one
or more channel configuration words and the channel enable status
bits are set, the channel status LEDs go on and the module
continuously converts the analog input to a value within the range
you selected.
Each time a channel is read by the module, that data value is tested
by the module for a fault condition (i.e., open-circuit, over-range,
and under-range). If such a condition is detected, a unique bit is set
in the channel status word and the channel status LED blinks.
System Overview