What the 1794-ASB/E Does in a FLEX I/O System
The Allen-Bradley 1794-ASB/E is a Remote I/O (RIO) adapter module from the FLEX I/O / Bulletin 1794 family. It acts as the bridge between a Universal Remote I/O network and the FLEX I/O modules mounted beside it. One adapter supports up to 8 FLEX I/O modules on a single node, so a compact DIN rail assembly can serve a whole cluster of field signals.
This module is discontinued, with a discontinuation date of 2015-03-31. Rockwell Automation lists the 1794-AENT / 1794-AENTR (EtherNet/IP) or 1794-ACN15 (ControlNet) as replacements. If your line still runs a Universal RIO network, the 1794-ASB/E remains a practical spare. Please verify current lifecycle status and availability with Oil AutoTech before ordering.
Key Specifications That Drive the Buying Decision
Network Speed and Node Capacity
The adapter offers selectable RIO baud rates of 57.6, 115.2, and 230.4 Kbps. Higher baud rates shorten scan time on larger nodes, while lower rates tolerate longer cable runs. With up to 8 FLEX I/O modules per adapter assembly, you can size the node to the machine instead of the cabinet.
Power and Thermal Budget
The module runs on 24V DC nominal, with an input range of 19.2-31.2V DC, and draws 330mA at 24V. Power dissipation is 4.6W. Those figures matter when you calculate the load on an existing 24V DC supply and the heat load inside a sealed enclosure.
Isolation and Mounting
Isolation is rated 50V continuous, type-tested at 750V DC for 60 seconds. The module mounts on a DIN rail, and its dimensions are 87 x 68 x 69mm. The operating temperature range is 0 to 55 C.
Where This Adapter Still Earns Its Place
Legacy Oil and Gas Skids
Many upstream and midstream skids still communicate over Universal RIO. A 1794-ASB/E lets you keep those skids running without a full control system migration. Fast-dispatch spares for oil, gas and industrial automation keep unplanned downtime short.
Distributed I/O in Process Plants
Because one adapter handles up to 8 modules, you can place I/O close to valves, transmitters, and motors. That cuts field wiring and shortens commissioning time.
Staged Upgrades
If you plan to move to EtherNet/IP later, the 1794-ASB/E buys time. Run the existing RIO node now, then migrate to the listed replacement when the budget and schedule allow.
Installation and Setup Notes
Snap the adapter and its terminal bases onto a DIN rail, then link the bases to form the FlexBus backplane. Each I/O module requires a 1794-TBx terminal base for field wiring and backplane connection. Set the RIO baud rate to match the network, and confirm the node address before power-up. Follow the manufacturer’s installation manual for all wiring and configuration steps.
Maintenance and Reliability
Inspect the DIN rail mounting and terminal base connections periodically. Check for loose field wiring and dust buildup that could raise the internal temperature. Keep the enclosure within the 0 to 55 C operating range. Because the module is discontinued, hold at least one spare on the shelf. That single spare often costs less than a day of lost production.
Compatibility and Integration
The 1794-ASB/E connects FLEX I/O modules to a Universal Remote I/O network. Integration Note: wiring into such networks may require an external gateway or connection module. Confirm cables and gateways with your supplier before you order.
What to Verify Before You Buy
- Confirm your network is Universal RIO, not EtherNet/IP or ControlNet.
- Count your I/O modules: the adapter supports up to 8.
- Check your 24V DC supply can carry the 330mA load.
- Confirm the 87 x 68 x 69mm footprint fits your DIN rail space.
- Ask about the listed replacements if you plan to migrate.
Oil AutoTech offers hands-on technical selection help and quick worldwide delivery on FLEX I/O spares. Contact Oil AutoTech today for pricing and availability.
Frequently Asked Questions
Is the 1794-ASB/E still in production?
No. It is discontinued, with a discontinuation date of 2015-03-31. Verify availability with Oil AutoTech before ordering.
What replaces the 1794-ASB/E?
Rockwell Automation lists the 1794-AENT / 1794-AENTR (EtherNet/IP) or 1794-ACN15 (ControlNet) as replacements.
How many FLEX I/O modules can one adapter support?
Up to 8 FLEX I/O modules on a single node.
What baud rates does it support?
Selectable RIO baud rates of 57.6, 115.2, and 230.4 Kbps.
What power does it need?
24V DC nominal, 19.2-31.2V DC range, drawing 330mA at 24V.
