DH+ and Remote I/O after the 1756 bridge modules: what changed and what the options are
If a ControlLogix in your plant talks to older hardware over Data Highway Plus or Remote I/O, it does it through a 1756-DHRIO or a 1756-RIO. Both are now discontinued.
The DHRIO went first, on December 31, 2024. The RIO followed on December 31, 2025 — and on that one, Rockwell's lifecycle listing gives the replacement as "No planned RA replacement." Not a migration part number. Nothing.
That matters more than it sounds, because those two modules are how a modern controller keeps talking to hardware installed decades earlier. 1771 racks on Remote I/O. PLC-5s and PanelViews on DH+. A lot of plants bought a ControlLogix specifically so they would not have to rip the old network out, and the bridge module is the entire reason that worked.
The two dates
| Module | What it does | Discontinued | Rockwell's replacement category |
|---|---|---|---|
| 1756-DHRIO | ControlLogix DH+ / Remote I/O comms module | 2024-12-31 | Engineering Replacement |
| 1756-RIO | ControlLogix Remote I/O scanner module | 2025-12-31 | "No planned RA replacement" |
Lifecycle information on this page was last verified against Rockwell Automation's published product pages on August 17, 2026.
The options, ranked honestly
1 · Count what you run and buy the spares now. Count the DHRIO and RIO modules in service, add the spares you'd want, and source them. No engineering, no downtime — you just spend money.
2 · Put DH+ and Remote I/O onto EtherNet/IP with a protocol gateway. Purpose-built converters bridge a ControlLogix to legacy DH+ and/or RIO networks. Minimal software configuration, and no existing Allen-Bradley hardware has to be replaced or reconfigured. Available with one to three DH+/RIO ports plus EtherNet/IP.
3 · Convert the 1771 I/O to EtherNet/IP. Swing-arm adapters or remote I/O conversion modules replace 1771 racks without rewiring field devices from scratch. The modules and terminal bases stay; the adapter, the network and the controller configuration change. A real project with a real budget. (Flex I/O is the easier cousin here — that one is an adapter change from 1794-ASB to 1794-AENTR.)
4 · Full platform migration to ControlLogix or CompactLogix throughout, on its own schedule.
Meridian analysis — our read, not a manufacturer statement
We are not telling you which one is right for your plant. Options 3 and 4 depend on your specific application — that is a controls-engineering decision, not a catalog lookup. Confirm the scope with Rockwell Automation or a qualified controls professional.
What to check before you buy
- Series and revision letters, confirmed against the unit in your rack — some firmware revisions do not behave identically in every application
- For secondary-market listings: exact catalog number, condition, documentation, seller terms
When you should NOT buy
If you already hold a spare, you are covered. If those networks are scheduled to come out in the next two or three years, deep spares are wasted money.
What Meridian can do
New-surplus, tested-used or refurbished 1756-DHRIO and 1756-RIO, with condition, warranty and lead time stated on the quote. We do not hold stock, and we will not promise a unit before a supplier confirms it.
We can also supply the gateway route in option 2 — current-production protocol converters, configured for one to three DH+/RIO ports plus EtherNet/IP. Tell us how many ports and what sits on the other end and we will come back with a delivered price.
Depending on the equipment and requirement, Meridian may research sourcing, exchange, manufacturer-supported migration, or third-party service options. Availability and suitability must be verified for each request.
Need a 1756-DHRIO or 1756-RIO module, or a DH+/RIO gateway? Send the catalog number, quantity and required date to brian@meridiansources.com or call 713-305-9321. One delivered price, condition and warranty spelled out.
Critical-Spare Review — limited Phase 1 pilot
Not sure what your real exposure is? Send up to 5 catalog numbers and Meridian returns a preliminary lifecycle and sourcing review: verified lifecycle status and replacement classification for each, including the parts that don't warrant a spare.
- Maximum 5 catalog numbers per review.
- This is a limited Phase 1 pilot — a maximum of 3 free reviews will be delivered during Phase 1.
- The review is preliminary and is not an engineering certification; compatibility and suitability require separate verification.
- Meridian may not be able to source every submitted item.
Start at Submit a Part Request — include the catalog numbers in the request notes, or we will ask for the list after you reach out.
Related
Disclaimer
Lifecycle and replacement information is for preliminary planning. Compatibility may depend on firmware, hardware revision, wiring, programming, network architecture, safety requirements, and the specific application. A manufacturer-listed successor may require modification or migration and may not be a direct drop-in replacement. Suitability must be verified with the manufacturer or a qualified controls professional.
Sources
- Rockwell Automation product details — 1756-DHRIO (rockwellautomation.com/en-us/products/details.1756-DHRIO.html). Accessed August 12, 2026.
- Rockwell Automation product details — 1756-RIO (rockwellautomation.com/en-us/products/details.1756-RIO.html). Accessed August 12, 2026; re-verified August 17, 2026.
- SoftPLC Corporation — published DH+/RIO gateway listings (store.softplc.com). Accessed August 12, 2026.