Product Overview

The Allen-Bradley 1756-RIO is a specialized communication module engineered to bridge the gap between modern Rockwell Automation ControlLogix controllers and legacy Allen-Bradley Remote I/O (RIO) networks -1-3-8. As a member of the Bulletin 1756 ControlLogix I/O family, this single-slot module enables seamless data exchange between a ControlLogix processor and existing RIO field devices, including 1771 I/O racks and specialty adapter modules, without requiring a complete hardware overhaul -4-8. The Allen-Bradley 1756-RIO is a critical component for system modernization projects, allowing plants to preserve significant investments in existing field wiring, sensors, actuators, and termination panels while upgrading the central control platform -4-7.

The Allen-Bradley 1756-RIO is distinguished by its exceptional flexibility, as it can be configured to operate in one of two modes: Scanner or Adapter -1-3-8. In Scanner Mode, it acts as the master of the RIO network, controlling up to 32 physical remote adapter devices such as 1771-ASB modules and mapping their I/O data directly into the ControlLogix controller’s tag database -1-7-8. In Adapter Mode, the module allows a ControlLogix chassis to emulate a classic remote I/O rack, enabling it to be scanned by legacy PLC-5 or SLC 500 systems -7. This dual functionality provides exceptional flexibility for phased migration strategies. The 1756-RIO fully supports the RIO protocol’s discrete I/O scanning and block transfer (BT) mechanisms, handling not only simple digital points but also complex analog modules and intelligent devices that require large data transfers -7-8. The module is configured entirely within the Studio 5000/RSLogix 5000 environment, presenting RIO data as standard tags and eliminating the need for low-level messaging instructions -7.

 

Technical Specifications

Parameter Name	Value
Product Model	1756-RIO
Manufacturer	Allen-Bradley / Rockwell Automation
Product Type	Remote I/O Communication Module
Series	ControlLogix 1756
Operating Modes	Scanner / Adapter (Selectable)
Number of RIO Ports	1
Supported Communication Rates	57.6 Kbps, 115.2 Kbps, 230.4 Kbps -1-3
Maximum Physical Racks (Scanner Mode)	32 -1-7
Supported Cable	Belden 9463 Twinaxial (Blue Hose) -6-8
Maximum Cable Length (57.6 Kbps)	3048 m (10,000 ft) -12
Maximum Cable Length (115.2 Kbps)	1524 m (5,000 ft) -12
Maximum Cable Length (230.4 Kbps)	762 m (2,500 ft) -12
Backplane Current Draw (5.1V DC)	450 mA -1-6-8
Backplane Current Draw (24V DC)	5 mA -1-6-8
Power Dissipation	2.5 W -1-6-8
Thermal Dissipation	8.5 BTU/hr -1-8
Isolation Voltage	50V Continuous (RIO port to backplane) -1-6-8
Slot Width	1 -1-6
Module Location	Any slot in 1756 ControlLogix chassis -8
Operating Temperature	0 to 60 °C (32 to 140 °F) -6-8
Non-Operating Temperature	-40 to 85 °C (-40 to 185 °F) -6
Relative Humidity	5 to 95% (non-condensing) -6
Enclosure Type	Open-style -1-6
North American Temperature Code	T4A -1-6

 

Main Features and Advantages

Dual-Mode Flexibility for Seamless Migration: The 1756-RIO can be configured as a Scanner to act as the master of the RIO network, scanning up to 32 remote adapter devices and mapping their data directly into the ControlLogix controller’s tag database -7-8. In Adapter Mode, the module allows a ControlLogix chassis to emulate a classic remote I/O rack, enabling it to be scanned by legacy PLC-5 or SLC 500 systems -7. This dual functionality provides exceptional flexibility for phased migration strategies, allowing plants to upgrade their control platform incrementally while maintaining compatibility with existing infrastructure.

Comprehensive Legacy I/O Integration: The 1756-RIO fully supports the RIO protocol’s discrete I/O scanning and block transfer (BT) mechanisms, handling not only simple digital points but also complex analog modules and intelligent devices that require large data transfers -7-8. By reusing existing field wiring and termination panels, the 1756-RIO significantly reduces the cost and downtime associated with full system replacements. It supports all possible partial rack combinations and can automatically update block transfers at all possible locations -8.

Seamless ControlLogix Integration: Configured entirely within the Studio 5000/RSLogix 5000 environment, the 1756-RIO presents RIO data as standard tags in the controller, eliminating the need for low-level messaging instructions and making the legacy network appear as an integral part of the modern control system -7. The module’s status is fully visible through the software, simplifying diagnostics and maintenance. The 1756-RIO supports up to 10 scheduled I/O connections, ensuring deterministic data exchange for time-critical applications -1-8.

Robust Diagnostic and Status Indication: The 1756-RIO features three status indicators (RIO, CLX, OK) and a 4-character alphanumeric display that provide comprehensive diagnostic information about the module’s operational state and network health -6-12. The RIO indicator displays the status of the remote I/O network connection, the CLX indicator shows the status of communication with the ControlLogix processor, and the OK indicator reflects the module’s internal health -12. This extensive diagnostic capability enables rapid troubleshooting and minimizes downtime.