Allen-Bradley 1771-DCM | PLC 5 Direct Communication Module

Product Overview

The Allen-Bradley 1771-DCM is a Direct Communication Module (DCM) designed for PLC 5 systems. It enables seamless communication between supervisory and local processors using a serial interface with Remote I/O (RIO) protocol. This module supports both discrete and block data transfer, ensuring reliable and efficient data exchange in industrial automation environments.

Supporting discrete transfer for up to eight words and block transfer for up to 64 words with one status word, the 1771-DCM optimizes data handling across the backplane and remote I/O networks. Its compact design fits a single slot on the 1771 I/O chassis, facilitating easy installation while maintaining robust performance.

With a communication rate of 57.6 Kbaud for distances up to 10,000 feet and 115.2 Kbaud for up to 5,000 feet, this module ensures fast and reliable signal transmission. Advanced diagnostic indicators monitor power, serial communication, backplane communication, and module faults to simplify maintenance and troubleshooting.

The module supports protected data transfer, preventing block transfer until the previous operation completes. Installation requires Belden 9463 or equivalent cable, and keying bands between pins 2–4 and 16–18 ensure correct placement in the I/O chassis.

Technical Specifications

Features and Benefits

• Dual Transfer Modes: Supports discrete and block transfers for flexible data handling.

• High-Speed Communication: 57.6 Kbaud and 115.2 Kbaud options for reliable long-distance connectivity.

• Diagnostic Indicators: Monitors power, communication, and module faults for simplified troubleshooting.

• Compact Installation: Requires only one slot on the 1771 I/O chassis, conserving space.

• Protected Data Transfer: Prevents block transfers until previous transfers complete, ensuring data integrity.

• Wide Operating Range: Functions reliably across industrial temperature and humidity extremes.

Applications

• Data exchange between supervisory and local PLC processors.

• Industrial automation systems requiring reliable Remote I/O communication.

• Integration into PLC 5 control systems for process monitoring.

• Block or discrete data transfer in complex industrial networks.

FAQ

Q1: What communication protocol does the 1771-DCM use?
It uses Remote I/O (RIO) protocol for serial communication with PLC processors.

Q2: How many words can the module transfer in block mode?
Up to 63 words plus one status word in block transfer mode.

Q3: What is the maximum communication distance?
57.6 Kbaud up to 10,000 ft or 115.2 Kbaud up to 5,000 ft using proper cabling.

Q4: What cable is required for installation?
Belden 9463 or an equivalent communication cable is required.

Q5: Can it prevent incomplete block transfers?
Yes, the module supports protected data to prevent block transfer until the previous transfer completes.