Rockwell Automation 1790D-NOV2/TNOV2 CompactBlock LDX Analog Modules - Manual (Page 15)

Publication 1790-UM001A-EN-P - March 2002
Overview 1-5
Module Operation
Input Module
The input module’s input circuitry consists of four analog inputs
multiplexed into a single analog-to-digital (A/D) converter. The A/D
converter reads the selected input signal and converts it to a digital
value that is presented to the network. The multiplexer sequentially
switches each input channel to the module’s A/D converter. Figure 1.2
on page 1-5 shows a block diagram of the circuitry.
Figure 1.2
Each time the input module reads a channel, the module tests that
analog data value for an overrange or underrange condition. If such a
condition is detected, a unique bit is set in the channel status word.
The channel status word is described in Chapter 4, Module Data,
Status, and Channel Configuration for Analog Output Modules.
43219
Isolation
Signal
Control
Data
Microcontroller
Optocouplers
DeviceNet XCVR
Input 0
Input 1
Input 2
Input 3
Select
24V dc
Field
Power Analog
power
supply
Analog
power
A/D
M
ul
tip
le
xe
r