Quick Sizing & Sourcing Snapshot
- Manufacturer: GE Fanuc (Emerson Machine Automation)
- Part Number: IC697BEM731
- System Platform: Series 90-70 PLC / PACSystems RX7i
- Hardware Type: Bus Controller Module (Single-Port Genius Bus)
- Architectural Role: Plugs into the VME backplane of a 90-70 CPU rack to act as the master interface for a Genius Bus network, communicating with up to 31 remote devices (Blocks, BIUs, DCMs).
- Key Specificifications: 1 Genius Port (Twinaxial), 31 Devices Max, 153.6 kbps, VMEbus Interface.
System Architecture & Operational Principle
The resides at Purdue Level 2, occupying a standard slot in a Series 90-70 CPU rack (e.g., IC697CHS771). It serves as the “Gateway” between the VME-based CPU (e.g., IC697CPU772) and the Genius Bus (Level 1/2 field network).
Upstream, it connects to the CPU via the VME P1/P2 Backplane. The CPU writes output data to the BEM731’s dual-port memory, and the BEM731 interrupts the CPU when new input data arrives.
Downstream, it drives a Genius Bus via a single Twinaxial Cable Port (50 Ohm characteristic impedance). It operates as the Bus Controller (Master), initiating the token-passing sequence at 153.6 kbps. It supports up to 31 remote devices (Slaves) on that single drop: this includes Genius Blocks (IC660BBAxxx), BIU Stations (IC670GBI002), and DCMs.
The “731” is the Single-Port variant. It is used when you have one string of devices. If you need two independent Genius networks (e.g., one for the turbine deck, one for the balance-of-plant), you use the IC697BEM713 (Dual-Port). Configuration (Station Numbers, I/O Data Tables) is done via the PLC programming software (Proficy Machine Edition / Logicmaster 90) or the Hand-Held Monitor (HHP). It supports Redundant BEM713s in CPU hot-standby pairs, but the 731 is typically used in simplex architectures or as the primary port in a 713 setup.
Core Technical Specifications
- Port Count: 1 Port (Twinaxial, Female BNC or Screw Terminal style depending on sub-rev)
- Device Capacity: 31 Devices (Per Port)
- Bus Speed: 153.6 kbps (Fixed Genius Standard)
- Cable Type: Shielded Twinaxial (50 Ohm, RG-58/U or equivalent)
- Max Distance: 7,500 ft (2.3 km) (Total daisy-chain length, depends on cable/termination)
- Backplane Interface: VMEbus (Accesses CPU Memory via VME)
- Indicators: MOD OK (Module Healthy), BUS ACT (Traffic), COMM (Port Active), FAULT (Error)
- Config Storage: Non-Volatile RAM (Configured via CPU / HHP)
- Isolation: 1500V AC (Bus to Backplane/Logic)
- Power: +5V DC (Backplane Sourced, ~1.2A typical)
- Operating Temp: 0°C to +60°C
