Spectrum Controls 1756sc-OF8H Series A - Manual (Page 17)

Chapter 1: Module Overview 3
Diagnostic LEDs
The modules contain diagnostic LEDs that help you identify the source of
problems that may occur during power-up or during normal operation.
Power-up and diagnostics are explained in Chapter 9, Testing Your
Module.
System Overview
The modules communicate with the ControlLogix processor and receive
+5 Vdc and +24 Vdc power from the system power supply through the
backplane interface. You may install as many modules in the system as
the power supply can support.
The 1756sc-IF8H has 8 channels that can receive voltage and current
signals from volt or milliamp devices. When configured for volt or
milliamp analog inputs, the module converts the analog values directly into
floating point values. For those input types, the module assumes that the
input signal is linear prior to input into the module.
The 1756sc-OF8H has 8 channels that can output volt or millivolt signals
to drive field sensors.
Both modules support HART communication. Communication is
independent of the analog acquisition and control phase.
System Operation
At power-up, the modules check internal circuits, memory, and basic
functions. During this time the Cal LED remains on. If the module does
not find any faults, it turns off the Cal LED.
After completing power-up checks, the modules wait for a connection to
an owner controller then valid channel configuration data from your ladder
logic program. After channel configuration data is transferred, and one or
more channels are enabled, the module channels are available to your
ladder program.
Each time the 1756sc-IF8H reads an input channel, the module tests that
data for a fault, i.e. over-range, or under-range condition. If it detects an
open-circuit (wire off), over-range or under-range condition, the module
sets a unique bit in the status tags.