Owner’s Guide 0300199-01 Rev. D
Chapter 1
Module Overview
This chapter describes the 1756sc-CTR4 and 1756sc-CTR8 and the conformally
coated 1756sc-CTR4/1756sc-CTR8K counter modules and explains how the
ControlLogix controller reads analog input data from the modules. Other than the
conformal coating, the modules are identical so all information applicable to the
earlier modules applies to the K versions. Read this chapter to familiarize
yourself further with counter module. This chapter covers:
• General description and hardware features.
• An overview of system and module operation.
This module is designed exclusively for use in the Allen-Bradley ControlLogix
1756 I/O rack systems. The module reads AC and DC pulse information from
external sensors and stores the data in its image table for retrieval by all
ControlLogix processors.
Following is a list of features available on the CTR8 module that allow their use
in a wide variety of applications:
• Removal and insertion under power (RIUP)−a system feature that allows you
to remove and insert modules while chassis power is applied.
• Producer/consumer communications−an intelligent data exchange between
modules and other system devices in which each module produces data
without having been polled.
• System timestamp of data–64-bit system clock places a timestamp on the
transfer of data between the module and its owner-controller within the local
chassis.
• IEEE 32-bit floating point format.
• On-Board Features, such as custom User Scaling, Analog and Digital
Filtering, and Under/Over Detection.
The 1756-CTR supports both AC and DC input signal types. The module input
type is configured on a channel-pair basis. Each pair must be configured for the
same input type.
The module fits into any single slot for I/O modules in a ControlLogix modular
system. The module has a unique generic profile which may be configured using
your RSLogix 5000 programming software. The module uses one removable
terminal block that provides connections for the eight input channels. The
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