Description:The Allen-Bradley 1785-CHBM (also known as 1785-CHBM/A) is a Hot Backup Memory Cartridge designed for the PLC-5 series of programmable controllers. It is a critical component for building redundant (hot backup) systems, providing 100K words of non-volatile memory to mirror the program and data from a primary processor to a standby processor. When used in conjunction with the 1785-BCM (Backup Communication Module), it enables seamless failover in mission-critical industrial applications, ensuring continuous operation in the event of a primary controller failure.Application Scenarios:In a chemical processing plant, a critical reactor control system cannot tolerate any downtime. A PLC-5 redundant system is deployed using two 1785-L40B processors. Each processor is equipped with a 1785-CHBM memory cartridge and connected via a 1785-BCM module. The primary processor continuously updates the 1785-CHBM in the standby unit. During a scheduled maintenance test, the primary processor is powered down. The 1785-CHBM allows the standby processor to take over control within milliseconds, maintaining the reactor temperature and pressure without interruption, preventing a costly batch loss and potential safety incident.
Parameter:
| Parameter | Specification |
|---|---|
| Product Model | 1785-CHBM / 1785-CHBM/A (Hardware Revision) |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Category | Hot Backup Memory Cartridge / Redundancy Module |
| Compatible Systems | PLC-5 Enhanced & ControlNet Processors |
| Memory Capacity | 100K Words (Non-Volatile User Memory) |
| Memory Technology | EEPROM (Electrically Erasable Programmable Read-Only Memory) |
| Write Protection | Configurable via Physical Jumper (Remove to Protect) |
| Key Processors | 1785-L20B/C, L40B/C, L60B/C, L80B/C, L20E, L40E, L60E, L80E |
| Redundancy Partner | Must be used with 1785-BCM (Backup Communication Module) |
| Operating Temperature | 0°C to 60°C (32°F to 140°F) |
| Storage Temperature | -40°C to 85°C (-40°F to 185°F) |
| Relative Humidity | 5% to 95% (Non-Condensing) |
| Vibration/Shock | Rated for 30G Operating Shock, Industrial Environment |
| Certifications | cULus, CE, CSA, C-TICK (Industrial Emissions) |
Technical Principles and Innovative Values:
- Innovation Point 1: Real-Time State Mirroring: The 1785-CHBM is not a simple storage card; it is an active component in a PLC-5 hot backup system. It works with the 1785-BCM to continuously synchronize the entire user program and data table (including timers, counters, and registers) from the primary processor to the backup processor. This ensures that at the moment of failover, the backup controller has the exact same “state” as the primary, allowing for bumpless transfer of control.
- Innovation Point 2: Non-Volatile Data Security: The cartridge utilizes EEPROM technology to retain the program and data even during a complete power loss. This is crucial for processes that require data historization or must resume from the exact point of interruption. The physical write-protect jumper provides an additional layer of safety, preventing accidental overwrites of the critical control logic during maintenance operations.
