1785-KEA Ser B (PU)

Allen Bradley Bulletin 1785 | Serial Communication Module

Allen Bradley Bulletin 1785 | DH+/RIO Communication Interface Module, asynchronous serial to DH+ or RIO bridge, Series B

The Allen-Bradley 1785-KEA is a high-performance communication interface module designed for the 1771 Universal I/O platform. It serves as a critical bridge between asynchronous serial devices and the PLC-5 control environment, allowing RS-232-C, RS-422-A, or RS-423-A compatible devices to communicate seamlessly over Data Highway Plus (DH+) or Remote I/O (RIO) networks. It is a vital component for integrating third-party computers, terminals, or specialized controllers into a centralized Allen-Bradley automation architecture.

This Series B module features a versatile serial port on the front panel that supports selectable baud rates ranging from 110 bps to 19.2 kbps. The network side of the module is highly configurable via internal DIP switches, allowing maintenance personnel to set the DH+ station address or RIO rack address without the need for specialized programming software. This flexibility makes it an ideal solution for data collection, system monitoring, and cross-platform communication in legacy PLC-5 systems.

The 1785-KEA is designed for ease of use and rapid diagnostics, featuring a set of front-panel status LEDs (Active, Adapter Fault, and Serial Port Status) that provide immediate visual feedback on communication health. It occupies a single slot in any standard 1771 chassis and manages all protocol conversion and data framing locally, offloading the communication processing burden from the main PLC-5 processor to ensure deterministic control performance.

Built for the rigors of heavy industrial environments, the module operates reliably between 0–60°C (32–140°F) in non-condensing humidity up to 95%. It draws 1.2A of current at 5VDC directly from the chassis backplane. The assembly is engineered to withstand significant operational shock and vibration and is UL listed and CSA certified, meeting the essential standards for safety and reliability in global industrial machinery and process control applications.

Key Specifications:

  - Function: Serial to DH+ or Remote I/O Bridge
  - Serial Protocols: RS-232-C, RS-422-A, RS-423-A
  - Network Support: Data Highway Plus (DH+) or Remote I/O (RIO)
  - Baud Rates: 110 bps to 19.2 kbps (Serial)
  - Backplane Current: 1.2A @ 5VDC
  - Platform: 1771 Universal I/O (PLC-5)
  - Series: B