Description
- Model: IC697BEM731Z
- Brand: GE Fanuc (Emerson)
- Series: Series 90-70 PLC
- Core Function: Interfaces the 90-70 CPU with a Genius I/O serial bus
- Product Type: Genius Bus Controller (GBC)
- Key Specs: 153.6 Kbaud / 76.8 Kbaud / 38.4 Kbaud | Supports 31 Devices | Hot-Swappable
- Bus Speed: Selectable (153.6 Kbaud standard; lower for longer distances)
- Device Capacity: Up to 31 Genius I/O blocks or other controllers per bus
- Maximum Distance: Up to 7,500 feet (2,286 meters) at 38.4 Kbaud
- Diagnostics: Comprehensive internal and bus-level fault reporting
- Redundancy: Supports GBC redundancy for high-availability systems
- Configuration: Set via MS-DOS based Logicmaster 90 or Proficy Machine Edition
- Indicators: OK (Green), COMM (Yellow) for bus activity
- Power Consumption: 1.2 Amps @ 5V DC (from backplane)
GE IC697BEM731Z
Application Scenarios & Pain Points
Engineering Pain Points: In a Genius I/O network, the IC697BEM731Z is a “master” that handles the timing of the entire bus. The biggest integrator “pitfall” is Shield Grounding and Termination. Genius bus is a daisy-chain serial network; if you don’t have exactly two 75, 100, or 150-ohm terminators (matching your cable type) at the ends of the run, you will experience “No Device Present” errors. Furthermore, the “Z” version indicates a later revision with improved components; mixing older non-Z and Z modules in a redundant pair can sometimes lead to synchronization jitter.
Typical Application Scenarios:
- Distributed I/O Control Managing large clusters of GE Genius I/O blocks across a massive manufacturing floor, reducing the need for miles of individual signal wiring.
- Redundant PLC Systems Using two IC697BEM731Z modules in separate 90-70 racks to provide a bumpless failover for critical infrastructure like water treatment or power plants.
- Drive System Integration Interfacing the PLC with GE variable speed drives that use the Genius protocol for high-speed setpoint delivery.
- Data Highway Bridging Allowing a Series 90-70 CPU to communicate with older Series Six or Series Five PLCs that still reside on a Genius network.
The “Flickering Bus” Case Study
Background: A steel mill was using an IC697BEM731Z to control a series of remote I/O blocks on a rolling line. Randomly, the entire bus would “reset,” causing the line to E-stop.
Problem: We checked the GBC diagnostics and saw a high “Bus Error” count. Upon physical inspection, we found the terminator at the last block was loose. However, the root cause was the baud rate. The cable run was nearly 3,000 feet, and they were trying to run it at 153.6 Kbaud.
Solution: We cleaned the connections, tightened the terminators, and dropped the baud rate to 76.8 Kbaud in the hardware configuration.
Result: The bus became rock-solid. Integrator’s Lesson: Sometimes “slower is better” when it comes to long-distance serial communication. Don’t push the max speed if your cable environment is electrically noisy.
GE IC697BEM731Z
Compatible Replacement Models
| Original Model | Related/Replacement | Compatibility | Note |
| IC697BEM731Z | IC697BEM731 | ✅ Direct Replace | “Z” is the newer hardware revision; same function |
| IC697BEM731Z | IC660ELB931 | ❌ Incompatible | This is an PC-based Genius Interface, not for PLC racks |
| IC697BEM731Z | IC693BEM331 | ❌ Incompatible | This is for the Series 90-30 PLC (different form factor) |
Integrator’s Tip: If you are migrating away from the 90-70 system, you can use a GE RX3i PBM300 to bridge your old Genius I/O blocks to a modern PACSystems controller. This allows you to keep your expensive field wiring while upgrading the “brain.”
Troubleshooting Quick Reference
| Symptom | Possible Cause | Related Part | Action |
| “OK” LED Off | Backplane Power Fault | ⚠️ Medium | Check the 90-70 Power Supply; reseat GBC module |
| “COMM” LED Off | No Bus Activity | ❌ Wiring | Check for broken serial cable or missing CPU config |
| Yellow COMM Flashing | Configuration Mismatch | ❌ Software | Ensure the Device IDs in the PLC match the physical I/O blocks |
| Periodic Bus Resets | EMI / Noise Interference | ❌ External | Verify shield is grounded at one end only; check terminators |
Field Note: …If you’re replacing this module, make sure you know the SBA (Serial Bus Address). The GBC is usually SBA 31. If you accidentally set it to an address already taken by a field block, the bus will crash immediately.
GE IC697BEM731Z
Strategic Quality Assurance (Our SOP)
- Bus Loopback Test: We connect the module to a test Genius I/O block and verify data transfer at all three baud rates (153.6K, 76.8K, 38.4K).
- Redundancy Validation: In a dual-GBC setup, we verify the module can correctly “hand over” the bus mastership without losing I/O states.
- Backplane Stress: The module is run in a 90-70 rack for 8 hours to ensure no thermal drift in the 5V power consumption.
- Physical Inspection: Verified for clean edge-connectors and no signs of component aging on the IC697BEM731Z board.
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