GE IC687BEM731-AB: Ethernet Interface Module for Series 90-70 PLC

Product Description

The GE IC687BEM731-AB is an Ethernet communications interface module for the GE Series 90-70 programmable logic controller (PLC). This module serves as a critical network gateway, enabling the PLC to communicate over standard 10 Mbps Ethernet networks. The GE IC687BEM731-AB allows the Series 90-70 CPU to exchange data with other controllers, human-machine interfaces (HMIs), supervisory control and data acquisition (SCADA) systems, and programming workstations. It implements the GE SRTP (Serial Real-Time Protocol) for peer-to-peer communication and supports standard Ethernet protocols like TCP/IP and UDP for integration with IT systems. The reliable performance of the GE IC687BEM731-AB was essential for integrating these robust legacy controllers into networked automation architectures.

Product Parameters

• Product Type: Ethernet Communication Interface Module
• Manufacturer: GE (General Electric) / Emerson
• Part Number: IC687BEM731-AB
• Compatible PLC Series: Series 90-70
• Network Standard: 10BASE-T Ethernet (IEEE 802.3)
• Data Rate: 10 Mbps.
• Connector: RJ-45.
• Protocols: Supports GE’s SRTP (for 90-Series PLC inter-communication) and standard TCP/IP and UDP/IP sockets.
• Configuration: Configured via DIP switches on the module for node ID and via the PLC programming software (Proficy Machine Edition or Logicmaster) for IP address and other parameters.
• Mounting: Plugs into a dedicated communication module slot in the Series 90-70 rack.

Advantages and Features

The primary advantage of the GE IC687BEM731-AB was its ability to bring mainstream Ethernet connectivity to the powerful Series 90-70 platform, extending its lifespan and integration capabilities. It enabled reliable, deterministic data exchange between 90-70 PLCs over a local area network (LAN) using SRTP. The module also allowed the PLC to be integrated into larger, heterogeneous systems via standard TCP/IP protocols. Its configuration via both hardware switches and software provided flexibility for network setup. The robust industrial design of the GE IC687BEM731-AB ensured reliable operation in plant floor environments.

Application Cases in Various Fields

This module was used to network Series 90-70 controllers in mid-to-large scale applications. In Automotive Manufacturing, the GE IC687BEM731-AB allowed multiple 90-70 controllers on a paint shop or body shop line to share production data and synchronize operations. Within Water Treatment Facilities, it enabled communication between process area PLCs and a central SCADA system. For Material Handling in distribution centers, it networked controllers for conveyors, sorters, and AS/RS systems. It was also common in Factory Automation cells where 90-70 PLCs needed to communicate with each other or with supervisory computers.

Comparisons with Competing Products

During its era, competing PLCs from Allen-Bradley (PLC-5 with Ethernet module) and Siemens (Simatic S5 with CP 1430) offered similar Ethernet connectivity. The GE IC687BEM731-AB was distinguished by its specific compatibility with the 90-70 series and its support for GE’s proprietary SRTP protocol for fast, deterministic peer-to-peer PLC communication. Compared to modern Ethernet modules offering 100/1000 Mbps and embedded web servers, this module is technologically basic, but it remains a vital component for maintaining and networking the extensive installed base of Series 90-70 systems.

Selection Suggestions and Precautions

1. Network Speed Limitation: The GE IC687BEM731-AB is a 10 Mbps device. Ensure your network infrastructure (switches) can autonegotiate down to 10 Mbps half/full duplex. Connecting it to a modern switch configured only for 100 Mbps may cause link failures.
2. IP Address and Node ID Configuration: The module requires two-part configuration: the hardware DIP switches set a unique “Station Number” for SRTP, and the software (in the PLC configuration) sets the IP Address, Subnet Mask, and Gateway. Both must be correctly set and unique on the network.
3. SRTP vs. TCP/IP Understanding: Clearly define the communication need. Use SRTP for fast, deterministic data exchange between GE 90-Series PLCs. Use TCP/IP sockets for communication with non-GE devices (HMI, SCADA, databases). The GE IC687BEM731-AB supports both, but they are configured differently in the ladder logic.
4. Legacy Software Requirement: Configuring the GE IC687BEM731-AB and programming the communication logic typically requires older software like Proficy Machine Edition (with 90-70 support) or the vintage Logicmaster 90. Ensure you have access to the correct software and cables.
5. Physical Connection and Diagnostics: Use standard CAT5 cable (straight-through). The module has status LEDs (PWR, OK, LINK, ACT) that are crucial for diagnostics. A steady OK LED indicates successful configuration and operation, while a flashing OK LED often indicates a configuration error or communication fault.