Section 1.7 System Overview; Module Power-Up; Module Operation - Spectrum Controls 1762sc-IF4OF4 User Manual

Section 1.7
System
Overview
NOTE
The module communicates to the controller through the bus interface. The
module also receives 5 VDC and 24 VDC power through the bus interface.
An external power supply is required for all 2-wire input transmitters.

1.7.1 Module Power-up

At power-up, the module performs a check of its internal circuits, memory, and
basic functions. During this time, the module status LED is blinking rapid green.
If no faults are found during power-up diagnostics, the module status LED 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 will
generate a PLC fault. Once a channel is properly configured and enabled, it
continuously converts the input or output data to a value within the range
selected for that channel.
Each time a channel is updated by the combo module, that data value is tested for
an open-circuit, short-circuit or "input/output data not valid" condition. If such a
condition is detected the channel data value will fail to a user-defined state
defined in the module configuration settings. For more details, refer to Chapter 3.
Using the module's input and output image table, the controller reads or writes
the two's complement binary data to and 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.

1.7.2 Module Operation

Input Channels
When the module receives the input from an analog device, the module's
circuitry multiplexes the input into an A/D converter. The converter reads the
signal and converts it as required for the type of input. If thermocouples are being
used, the module continuously samples the CJC sensor, and compensates for
temperature changes at the terminal block cold junction, between the
thermocouple wire and the terminal connector.
Output Channels
The module's output channel uses a digital-to-analog (D/A) converter to read the
digital output data from the controller and convert it to an analog output signal.
Chapter 1: Module Overview
User's Manual Pub. 0300247-01 Rev. D
1-5