Spectrum Controls 1794sc-IRT8I - Manual (Page 9)

Chapter 1: Module Overview 1-3
User's Manual Pub. 0300242‐01 Rev. A
program. In either case, the module configuration is stored in the memory of the
controller. Refer to your controller’s user manual for more information. The illustration
below shows the module’s hardware features.
Item Description
1 Module Catalog Number
2 Module key-switch position
3 Removable label
4 Power/Status LED
Section 1.6
System
Overview
The module communicates to the controller through the base unit bus interface. The
module also receives 5 and 24V dc power through the bus interface.
Note: An external power supply is required for all 2-wire transmitters.
1.6.1 Module Power-up
At power-up, the module performs a check of its internal circuits, memory and basic
functions. 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, it continuously
converts the input data to a digital value within the currently selected data range. Each
time a channel is read by the input module, that data value is tested by the module for an
over-range, under-range, or open-circuit condition. If such a condition is detected, a
unique bit is set in the channel status word. The channel status word is described in the
Input Data File in Chapter 3. Using the module image table, the controller reads the
two’s complement 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 made available to the control program.
Section 1.7
Module
Operation
The module measures each analog signal using a dedicated A/D converter for each
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3
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Figure 1-1