Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-DHRIO |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | DH+/RIO Communication Interface Module |
| Number of Channels | 2 (independently configurable) |
| DH+ Baud Rates (Channel A) | 57.6, 115.2, 230.4 Kbps |
| DH+ Baud Rates (Channel B) | 57.6, 115.2 Kbps |
| RIO Capacity per Channel | 32 logical rack connections or 16 block transfer connections |
| RIO Baud Rates | 57.6, 115.2, 230.4 Kbps |
| Backplane Current (5V) | 850 mA |
| Backplane Current (24V) | 1.7 mA |
| Maximum Power Dissipation | 4.5 W |
| Maximum Heat Dissipation | 15.4 BTU/hr |
| Insulation Voltage | 30 V continuous (basic insulation) |
| Operating Temperature | 0°C to 60°C (standard); -25°C to +70°C (XT variant) |
| Wiring | Copper twisted-pair, Belden 9463 recommended |
| Wire Size | 0.2–2.0 mm² (24–14 AWG) |
| Lifecycle Status | Discontinued (effective December 31, 2024) |
Main Features and Advantages
Dual-Channel Flexibility for Mixed Network Architectures: The 1756-DHRIO allows each channel to be independently configured as DH+ or RIO, enabling a single module to serve as both a DH+ bridge to legacy PLC-5 systems and an RIO scanner for remote I/O racks. This dual capability reduces the number of modules required in a ControlLogix chassis, conserving slots and simplifying network topology. Channel A is typically used for DH+ when programming terminal access is needed, as its front-panel connector supports direct connection.
Seamless Integration with Legacy Allen-Bradley Platforms: The 1756-DHRIO bridges ControlLogix controllers to PLC-5 and SLC 5/04 processors over DH+ networks, allowing message instructions (MSG) to exchange data between disparate controller families. This capability is critical for phased migration projects where new ControlLogix hardware must coexist with existing PLC-based control systems. The module also supports CIP bridging, enabling messages from Ethernet or ControlNet devices to reach DH+ nodes through the routing table.
High-Capacity RIO Scanning for Distributed I/O: When configured as an RIO scanner, the 1756-DHRIO supports up to 32 logical rack connections per channel, accommodating large distributed I/O systems with multiple remote adapters. The module distributes control so that each controller maintains ownership of its own I/O, supporting deterministic data exchange for time-sensitive applications. Block transfer capability (16 connections per channel) enables analog and specialty I/O modules to be integrated into the RIO network alongside discrete I/O.
Robust Routing and Gateway Functionality: The 1756-DHRIO can route messages through up to four networks and three chassis, allowing devices on DH+, ControlNet, Ethernet, and other networks to communicate as if locally connected. This routing capability eliminates the need for external gateway devices in many configurations, reducing hardware costs and points of failure. The module’s routing table is configured through RSLogix 5000 or Studio 5000 and must be carefully documented for maintenance and replacement purposes.
