GE IC687RCM711｜Redundancy Communications Module｜

IC687RCM711 is the core board of GE 90-70 that implements CPU Hot Standby redundant architecture, widely used in critical process control systems that do not allow downtime. The entire redundant system requires the configuration of two IC687RCM711 modules, one installed in the main controller rack and the other in the backup controller rack. The two modules are connected through dedicated differential redundant cables to establish an independent high-speed synchronization link, completing real-time mirror synchronization of programs, registers, I/O status, and system clock between the dual CPUs. When the main CPU experiences hardware failure or power failure, the backup CPU takes over control in milliseconds, achieving disturbance free system switching and uninterrupted production processes.
This module is only responsible for redundant synchronization and cannot be used as a CPU. It cannot directly drive on-site I/O, does not participate in Genius bus, does not occupy Ethernet communication bandwidth, and synchronizes data streams through independent hardware channels, which will not burden on-site business communication.
Detailed explanation of core functions
Dual CPU high-speed data mirror synchronization (HSB hot backup)
The module runs a dedicated differential synchronization protocol with an effective transmission rate of 500KB/s. It continuously copies all the running status, internal registers, and logical operation results of the main CPU to the backup CPU synchronously. The backup controller is always fully aligned with the main controller and is always in a hot ready state. Once the main unit fails, it will immediately be upgraded to the main controller, and the output logic will seamlessly connect to avoid process jumps and equipment malfunctions.
Supports two redundancy modes: single rack FIP redundancy and dual rack enhanced hot standby redundancy. In single rack mode, the primary and backup CPUs are installed in the same VME rack; The dual rack mode consists of two independent racks, with completely isolated hardware and stronger resistance to single point failures.
Manually force the switch button between primary and backup
The module panel is configured with physical buttons, and operation and maintenance personnel can manually trigger the main and backup switching during online maintenance. After pressing, the system will switch control to the backup CPU, reducing the original main CPU to the backup, making it convenient for online maintenance and replacement of faulty CPUs without shutting down the entire system; After the switch is completed, allow at least 10 seconds for the next switch to be executed to prevent frequent oscillation switching from causing system abnormalities.
Complete status LED diagnostic indication
The board has a total of 5 status indicator lights, which respectively indicate module power supply, operating status, primary/backup roles, synchronization link status, and fault alarms. The on-site control cabinet can quickly determine with the naked eye whether the module is powered on, the link is disconnected, the synchronization is normal, and which block is currently in the active main control. Fault information can also be uploaded to the PLC CPU, programming software, and upper HMI to read redundant system alarms, making it easier to locate the fault point and shorten downtime for troubleshooting.
Independent differential hardware communication link
Adopting non isolated differential signal transmission, it does not rely on PLC backplane bus, Genius fieldbus, or Ethernet network. Even if there is a storm or disconnection in the on-site network, the synchronization between the primary and backup CPUs is still not affected, ensuring the independent and reliable redundancy switching function.
Cable specifications: Dedicated RCM redundant cable, maximum cable length of 15 meters; It is recommended to control the FIP mode cable of a single rack within 0.9 meters to ensure stable synchronization timing.
Software configuration, no hardware dialing
All redundant parameters, primary and backup modes, and synchronization options of the module are configured and set in Proficy Logic Developer or early DOS programming software. The board does not have DIP dip switches, reducing the risk of manual setting errors. After the configuration is completed, download it to the PLC and automatically establish a primary backup synchronization link when powered on.
Hardware electrical specifications
Hardware form: VME bus standard, single slot half width module, occupying 1 slot in the rack
Backboard power supply: The rack backplane is powered by 5VDC, with a working current of 1.2A, and does not require external power supply
Connector: Two sets of interfaces on top and bottom of the module, one set connected to the RCM711 redundant cable at the opposite end; A set of VME backboards connected to the rack bus
Communication method: differential non isolated synchronous communication, effective rate of 500KB/s
Working temperature: 0 ℃~+60 ℃; Storage temperature -40 ℃~+85 ℃
Humidity: 5% -95% RH, no condensation, IP20 for use inside the control cabinet
Weight: Approximately 0.25kg
Certification: UL, CE Industrial Certification