Rockwell Automation 1771-N SERIES High Resolution Analog Module User Manual - Manual (Page 15)

Chapter
1
Publication 1771ĆUM127B-EN-P - December 2002
Overview of the High
Resolution Isolated
Analog Modules
This chapter gives you information on:
• features of the input/output modules
• how the modules communicate with programmable controllers
The high resolution isolated analog modules are intelligent block
transfer modules that interface analog signals with Allen-Bradley
PLC-3 and PLC-5 family programmable controllers that have block
transfer capability. Block transfer programming moves input data
words from the module’s memory to a designated area in the
processor data table in a single scan. It also moves configuration
words and output data from the processor data table to module
memory.
The N-series family includes modules with both analog inputs and
outputs on the same module. The modules use 16-bit
analog-to-digital converters and 14-bit digital-to-analog converters
for high resolution and accuracy. All of these modules require only a
single slot in the I/O chassis, and do not require an external power
supply.
Since the N-series modules are combination modules, with input and
output capabilities on the same module, block transfer reads from the
module are structured differently from dedicated input or output
modules. Normally, block transfer read information is contiguous,
and is stored in contiguous locations in the data block. N-series
modules transmit channel data on an individual basis with status
information in between. This results in non-contiguous blocks of
data in non-contiguous data locations. Care must be taken when
transferring this information. Additional programming may be
required.
IMPORTANT
Use with PLC-2 family programmable
controllers is not recommended. Refer to
chapter 3, page 3-2.
Input data is converted to a specified data type in a digital format to
be transferred to the processor’s data table on request. Output data is
converted to analog signals and sent to the appropriate output
channels. If real time sampling is selected, block transfer reads will
only occur at the time selected. Consequently, the minimum interval
between block transfer reads is the same as the total input update
time for each analog input module (25ms).
Chapter Objectives
Module Description