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Universal Remote I/O Link Overview 

The Allen-Bradley Universal Remote I/O Link connects the PLC and SLC processors to remote I/O chassis and a host of intelligent devices such as operator interfaces and ac and dc drives.
In addition to I/O, Allen-Bradley operator interfaces, ac and dc drive systems, intelligent sensing products, Computer Numerical Controllers (CNCs), and other devices are compatible with this link. Some products, such as PanelView Operator Terminals, have built in "adapter" capability, while other products, such as the 1336 drives, require optional "adapter" modules to put them on the link. Some products are installed in the 1771 I/O chassis and communicate over the chassis backplane to a Remote I/O Adapter, which communicates to the programmable controller's scanner. In addition, the 1784-PKTS communication interface card lets an ISA/EISA bus PC communicate directly with Allen-Bradley remote I/O devices.
Other companies offer products such as robotic and welding controllers, scales, and wireless modems that are compatible with the Universal Remote I/O Link as well. In total, there are approximately 100 devices available that can communicate on this link. By using these devices on the link, the user can speed up communication and allow the devices to work together to help improve quality while lowering integration, maintenance, and training costs.
For distributed processing, put a PLC-5 processor in "adapter mode" and install it in an I/O chassis where it can monitor its own resident I/O while communicating to a supervisory PLC-5 processor over the Universal Remote I/O Link. SLC processors can also be distributed on the link where they can control I/O while communicating with a supervisory processor via a 1747 Direct Communication Module.
For high-speed processing applications, an extended-local I/O link is available, which provides a parallel I/O link (the practical equivalent of processor-resident-chassis performance for I/O modules not placed in the processor's chassis). In addition, the Allen-Bradley ControlNet network, which provides deterministic, repeatable transfers of control data, is suitable for real-time, high-throughput applications.


- Uses transceivers communicating over a single channel.
- Uses standard PVC twinaxial cable (cat. no. 1770-CD) as the transmission medium.
- Uses a daisy-chain connection with a maximum length of 3,048m (10,000 ft).
- Operates at the data rates listed in Specifications. A 1/2-watt terminating resistor is required at each end of the trunk line to eliminate reflections. Error checking is done using standard CRC16 checks.
- Is based on the master/slave model. The controller's scanner is the master and the I/O chassis or adapter devices are slaves. The slave only responds when told to by the master.
- Provides transfer of a single unit (8, 16, or 32 bits) of I/O image data to/from each I/O module in each I/O chassis during each I/O scan. The size of the unit depends on the I/O addressing density selected at the I/O chassis. It can also provide block transfers of 64 words maximum to an individual I/O module (except when used with the 1747-SN).
- Lets Remote I/O Scanners connect to a maximum of 32 I/O chassis or other adapter-type devices on a single link. Devices built to original Universal Remote I/O specifications are compatible with those built to the new specifications. However, if any of the devices on a link are built to the original specifications, the limit is 16 devices on a single link. In any case, for a specific scanner, the number of adapter-type devices is limited by the I/O rack addressing capability of the scanner.

Universal Remote I/O Specifications
Communication Rate Distance meters (ft) Termination Resistor
57.6 kbit/s 3,048 (10,000) 150W 1/2W or 82.5W 1/2W
115.2 kbit/s 1,524 (5,000) 150W 1/2W or 82.5W 1/2W
230.4 kbit/s 762 (2,500) 82.5W 1/2W



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