Allen-Bradley 1769-SM2 DSI Modbus Module

Product Overview

The Allen-Bradley 1769-SM2 is a versatile Compact I/O communication module that enables seamless integration between CompactLogix or MicroLogix 1500 controllers and PowerFlex drives. By supporting both DSI and Modbus RTU protocols, the 1769-SM2 provides a cost-effective solution for distributed drive control. 

Technical Configuration

Dual-Protocol Versatility

The 1769-SM2 excels in multi-protocol environments. It supports a fixed 19.2 kbps DSI rate for Allen-Bradley drives and adjustable Modbus RTU speeds ranging from 300 to 38.4 kbps. This flexibility allows engineers to interface with a wide range of peripheral devices and legacy systems using a single hardware footprint.

System Integration

Designed for the CompactLogix platform, the 1769-SM2 draws power directly from the backplane (350mA @ 5V DC). Its small form factor supports DIN rail or panel mounting, making it ideal for space-constrained enclosures where efficient hardware density is critical for system performance.

Technical Specifications

Installation & Maintenance Guide

• Distance Limits: Maintain a maximum cable length of 10 meters when connecting the 1769-SM2 to PowerFlex drives to ensure signal integrity.
• Network Expansion: For Modbus networks, the 1769-SM2 supports a maximum distance of 1219 meters (4000 feet).
• Power Supply Distance: Do not install the 1769-SM2 module more than 4 slots away from the system power supply to prevent voltage drops.
• Environment: Ensure the installation area is free from corrosive vapors and meets the vibration resistance specifications of 5g.

Engineering Advantages

The 1769-SM2 eliminates the need for complex external gateways by providing native drive communication within the CompactLogix I/O bank. This tight integration allows for better diagnostic visibility and faster commissioning of PowerFlex drive systems. Its ability to host Modbus RTU traffic makes the 1769-SM2 a powerful tool for hybrid systems requiring both proprietary and open-standard communication.

Technical FAQs

Q1: Can the 1769-SM2 control multiple drives simultaneously?
A1: Yes, the 1769-SM2 features three channels that can independently interface with PowerFlex 4-Class or 7-Class drives depending on the configuration.

Q2: Does the 1769-SM2 require an external 24V power source?
A2: No. The 1769-SM2 is fully powered by the 1769 backplane via the 5V DC supply, drawing 0mA from the 24V DC bus.

Q3: Is the Modbus baud rate fixed like the DSI speed?
A3: No. While DSI is fixed at 19.2 kbps, the Modbus RTU communication speed on the 1769-SM2 is adjustable between 300 and 38,400 bps.

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