Allen-Bradley 1756-DHRIO — DH+/RIO Bridge & Scanner Module | ControlLogix Platform
Engineering Background: The 1756-DHRIO is a ControlLogix communication module developed by Rockwell Automation / Allen-Bradley, purpose-built to bridge modern ControlLogix controllers with legacy Data Highway Plus (DH+) networks and Remote I/O (RIO) device networks. It enables seamless integration of existing DH+ and RIO infrastructure into contemporary ControlLogix-based control architectures without requiring full system replacement.
Product Positioning: Designed for industrial automation engineers managing brownfield upgrades, the 1756-DHRIO eliminates costly rip-and-replace scenarios by providing a high-integrity communication bridge. It is the preferred solution for facilities running legacy PLC-5, SLC 500, or MicroLogix systems that must coexist with or migrate to ControlLogix platforms.
Complete Technical Specifications
- Catalog Number: 1756-DHRIO
- Platform: Allen-Bradley ControlLogix (1756 Chassis)
- Communication Ports: 2 × DH+ channels (Channels A & B), each independently configurable as DH+ or RIO
- DH+ Data Rate: 57.6 Kbps, 115.2 Kbps, 230.4 Kbps (selectable)
- RIO Data Rate: 57.6 Kbps, 115.2 Kbps, 230.4 Kbps (selectable)
- RIO Scanner Capacity: Up to 32 I/O racks (64 quarter-racks) per channel
- DH+ Node Address: 0–77 (octal), software configurable
- Backplane Current Draw: 1.0 A @ 5 VDC; 3.0 mA @ 24 VDC
- Power Dissipation: 5.0 W (max)
- Operating Temperature: 0 °C to +60 °C (32 °F to 140 °F)
- Storage Temperature: −40 °C to +85 °C
- Relative Humidity: 5% to 95% non-condensing
- Vibration: IEC 68-2-6 compliant
- Shock: IEC 68-2-27 compliant
- Certifications: UL, CE, C-Tick, FM Class I Div 2
- Module Weight: Approx. 260 g
- Dimensions: Standard 1756 single-slot module form factor
- Firmware: Field-upgradeable via RSLogix 5000 / Studio 5000
Proven Application Environments
- Brownfield plant upgrades: bridging legacy PLC-5 / SLC 500 DH+ networks to ControlLogix
- Remote I/O scanner for 1771 I/O racks and third-party RIO-compatible devices
- Multi-controller DH+ messaging (MSG instructions) across plant-floor networks
- Automotive assembly lines with mixed-generation Allen-Bradley control systems
- Oil & gas facilities requiring Class I Div 2 rated communication modules
- Water/wastewater SCADA systems integrating legacy field devices
- Food & beverage plants with phased automation modernization programs
- Mining and heavy industry with long-distance RIO cable runs
Engineering Advantages
- Dual Independent Channels: Each channel operates independently as DH+ or RIO, maximizing topology flexibility in a single module slot
- Non-Disruptive Integration: Preserves existing DH+ and RIO wiring infrastructure, reducing migration cost and downtime risk
- High Node Density: Supports up to 64 quarter-racks per RIO channel for large distributed I/O architectures
- Deterministic Communication: Token-passing DH+ protocol ensures predictable, collision-free data exchange
- Studio 5000 Native: Full configuration and diagnostics within Rockwell’s standard engineering environment
- Hot-Swap Capable: ControlLogix chassis supports module removal/insertion under power (RIUP) for maximum uptime
- Proven Reliability: Field-hardened design with 20+ years of global deployment history in mission-critical applications
System Architecture & Signal Flow
The 1756-DHRIO occupies a single slot in any 1756 ControlLogix chassis and communicates with the ControlLogix controller via the high-speed ControlLogix backplane. Each of the two external ports (Channel A and Channel B) can be independently configured:
- DH+ Mode: The module acts as a DH+ node, enabling MSG instruction-based peer-to-peer communication with PLC-5, SLC 500, and other DH+ nodes. Supports read/write, program upload/download, and diagnostics.
- RIO Scanner Mode: The module acts as the RIO scanner (master), polling up to 32 I/O racks. I/O data is mapped directly into the ControlLogix controller’s I/O tree for ladder logic consumption.
Both channels operate simultaneously and independently, allowing a single 1756-DHRIO to serve as both a DH+ bridge and an RIO scanner concurrently — a critical advantage in complex multi-network plant environments.
Sourcing & Quality Verification
- Source: Konmask.com sources 1756-DHRIO modules from authorized distributors and verified surplus channels with full traceability documentation
- Inspection Protocol: Each unit undergoes visual inspection, label verification, firmware version check, and functional power-on test prior to shipment
- Authenticity: Modules are verified against Rockwell Automation catalog specifications; counterfeit screening is performed on all incoming stock
- Condition: New, refurbished, and tested-used grades available — condition clearly stated on each listing
- Warranty: 12-month Konmask warranty covering manufacturing defects and functional failure under normal operating conditions
- Documentation: Certificate of conformance and test report available upon request
Procurement Process
- Confirm Part Number: Verify catalog number 1756-DHRIO and firmware revision requirement with your engineering team
- Request Quote: Contact [email protected] with quantity, required condition grade, and delivery timeline
- Order Confirmation: Receive proforma invoice with lead time, shipping options (DHL / FedEx / UPS express available), and payment terms
- Quality Hold: Unit reserved and final inspection completed before dispatch
- Shipment & Tracking: ESD-safe packaging with real-time tracking provided; export documentation included for international orders
- Post-Delivery Support: Technical assistance available for installation, configuration, and commissioning queries
Technical FAQ
Q: Can the 1756-DHRIO replace a 1756-DHRP?
A: No. The 1756-DHRP is a ControlNet-to-DH+ router; the 1756-DHRIO bridges DH+ and RIO networks to ControlLogix. They serve different network integration purposes.
Q: How many 1756-DHRIO modules can I install in one chassis?
A: Multiple modules can be installed in the same chassis, limited only by chassis slot count and backplane power budget. Each module provides two independent channels.
Q: Is the 1756-DHRIO compatible with all ControlLogix chassis sizes?
A: Yes — it is compatible with all 1756 chassis variants (4, 7, 10, 13, 17-slot) and all ControlLogix controller families (L6x, L7x, L8x series).
Q: What software is required for configuration?
A: RSLogix 5000 (v16+) or Studio 5000 Logix Designer. The module appears in the I/O tree and is configured via the module properties dialog.
Q: Can Channel A and Channel B run different protocols simultaneously?
A: Yes. Channel A can be configured as DH+ while Channel B operates as RIO scanner, or both can run the same protocol — fully independent configuration.
Q: What is the maximum DH+ network cable length?
A: Per Rockwell specifications, maximum DH+ trunk cable length is 3,048 m (10,000 ft) at 57.6 Kbps, decreasing with higher baud rates.
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