GE Automation & Controls IC693BEM331K Modbus Communication Interface Module - GE IC693BEM331K

Technical Dossier

Product Details And Specifications

GE IC693 Series Technical Notes

The GE IC693 series — commercially designated as the Series 90-30 PLC — is one of the most widely deployed programmable logic controller platforms in global heavy industry. Installed across petrochemical refineries, nuclear power auxiliary systems, offshore platforms, pulp and paper mills, and continuous process manufacturing facilities, the IC693 rack-based architecture established a benchmark for modular, scalable control in the 1990s and 2000s. Its 5-slot, 10-slot, and expansion rack configurations support mixed I/O and communication modules on a shared backplane bus, enabling system integrators to construct distributed control nodes with deterministic scan times. As of 2026, the IC693 series is in its end-of-life and long-term maintenance phase; GE Vernova (formerly GE Automation & Controls) has transitioned active development to the RX3i (IC695) platform. However, the installed base of IC693 systems remains substantial, and demand for spare modules — particularly communication interfaces such as the IC693BEM331K — continues across MRO (Maintenance, Repair & Operations) channels globally.

The Evolution of IC693 Architecture

The IC693 platform was introduced in the late 1980s as part of GE Fanuc Automation's Series 90 family, which encompassed the Micro (IC693), 90-30 (IC693), 90-70 (IC697), and later the RX3i (IC695) lines. The original IC693 backplane used a parallel bus architecture operating at 5 VDC logic levels, with module addressing determined by physical slot position. Early firmware revisions (pre-Rev. F) had limited support for floating-point math and structured text programming; these were progressively resolved through CPU module upgrades (IC693CPU311 → IC693CPU374).

Communication capability evolved in parallel: early deployments relied on RS-232 serial ports on the CPU module itself, while dedicated communication coprocessors (BEM series) were introduced to offload protocol handling — Modbus RTU/ASCII, Genius Bus, Ethernet TCP/IP, and DeviceNet — from the main CPU scan cycle. The IC693BEM331 and its revision variants (331A through 331K) represent the mature Modbus RTU/ASCII coprocessor implementation, supporting up to 32 Modbus slave devices per module with configurable baud rates from 1200 to 19200 bps.

Compatibility constraints are a critical operational consideration: IC693 CPUs require matching backplane revision levels, and mixing early-revision I/O modules with late-revision CPUs can produce bus arbitration faults. The IC693 platform is not electrically or software-compatible with the IC695 (RX3i) backplane; migration requires full rack replacement and Proficy Machine Edition project conversion.

IC693 Full Catalog & Functionalities (SKU List)

CPU Modules

• IC693CPU311: 6 KB user memory, 0.4 ms/K boolean, no floating point, basic Series 90-30 CPU.
• IC693CPU313: 12 KB user memory, enhanced instruction set, supports analog scaling.
• IC693CPU321: 32 KB user memory, floating-point math, expanded I/O addressing.
• IC693CPU331: 32 KB user memory, built-in RS-232/RS-485 serial port, Modbus master/slave via port.
• IC693CPU340: 240 KB user memory, Ethernet TCP/IP embedded, supports SRTP protocol.
• IC693CPU350: 240 KB user memory, dual Ethernet ports, enhanced diagnostics, high-speed counter support.
• IC693CPU360: 512 KB user memory, advanced motion coordination, expanded PID loop count.
• IC693CPU374: 512 KB user memory, embedded Ethernet, highest-performance IC693 CPU, supports C-block programming.

Communication Modules (BEM Series)

• IC693BEM331K: Modbus RTU/ASCII communication interface, supports up to 32 slave devices, RS-232/RS-485, configurable baud rate 1200–19200 bps. Revision K — final production revision.
• IC693BEM331: Base revision Modbus RTU/ASCII coprocessor; functionally equivalent to 331K with earlier firmware.
• IC693CMM311: Multi-protocol communication coprocessor, supports Modbus, DF1, and custom ASCII protocols via user-loaded firmware.
• IC693CMM321: Ethernet TCP/IP interface module, 10BASE-T, SRTP and Modbus TCP support.
• IC693DNM200: DeviceNet master/slave scanner, supports up to 64 nodes, explicit and I/O messaging.

Discrete Input Modules

• IC693MDL230: 8-point 120 VAC discrete input, isolated, standard density.
• IC693MDL240: 16-point 120 VAC discrete input, non-isolated, high density.
• IC693MDL241: 16-point 24 VDC discrete input, positive logic (source), standard wiring.
• IC693MDL260: 32-point 24 VDC discrete input, high-density, connector-based wiring.

Discrete Output Modules

• IC693MDL330: 8-point 120/240 VAC relay output, 2A per point, isolated contacts.
• IC693MDL340: 8-point 120 VAC triac output, 0.5A per point, zero-crossing switching.
• IC693MDL752: 16-point 24 VDC transistor output, positive logic (source), 0.5A per point.

Analog Modules

• IC693ALG220: 4-channel analog input, 4–20 mA / 0–10 VDC selectable, 12-bit resolution.
• IC693ALG390: 4-channel analog output, 4–20 mA / 0–10 VDC, 12-bit resolution.

Power Supply Modules

• IC693PWR321: 120/240 VAC input power supply, 30W output, standard IC693 rack power.
• IC693PWR330: 24 VDC input power supply, 30W output, for DC-powered panel installations.

Quality Control for the IC693 Range

IC693 modules present specific test challenges due to their backplane-dependent initialization sequence: a module cannot be fully validated in isolation without a functioning IC693 rack, CPU, and power supply. DriveKNMS employs dedicated IC693 test benches configured with IC693CPU350 or IC693CPU374 CPUs and IC693PWR321 power supplies to perform full functional validation.