Product Overview

The Allen Bradley 1785-MR provides high-speed, volatile program storage for the Allen Bradley PLC-5 controller platform. This 4K Word CMOS RAM Memory Cartridge expands the workspace available for active ladder logic execution, math instructions, and data table mapping. It interfaces seamlessly with the processor to allow rapid read/write cycles during standard machine control operations. We supply this product as 100% Brand New and Original, packed in static-shielded factory packaging to ensure optimal performance when updating or maintaining legacy plant automation systems.

Technical Specifications

Engineering Advantages

• High-Speed Processing Execution: The CMOS RAM architecture inside the 1785-MR delivers near-instantaneous read and write access times. This high-speed performance allows the PLC-5 processor to execute complex math calculations and rapid I/O updates without causing scan-time delays.

• Onboard Program Safeguards: A hardware-based write-protection jumper shields the cartridge from accidental modifications. Moving this jumper to the protected state blocks the software from overwriting critical operational code, preventing logic corruption during online edits.

• Seamless Complementary Backup: The module pairs directly with external EEPROM cartridges (such as the 1785-MJ or 1785-MK). Engineers can develop and fine-tune code in the fast-acting 1785-MR RAM module, then flash the finalized logic to a non-volatile cartridge for long-term power-off storage.

• Zero Footprint Integration: The cartridge plugs directly into the processor's dedicated internal slot. It draws all its required 5 V DC working current straight from the backplane, eliminating extra field wiring and conserving space on the control panel.

FAQs

• Does the 1785-MR retain data after I turn off the main PLC power?

  No. The 1785-MR uses volatile CMOS RAM, meaning it loses all stored programs when you remove the module from the chassis or power down the system. To prevent data loss, ensure your PLC-5 processor possesses a functional backup lithium battery or duplicate the code onto an EEPROM module.

• Can I install this memory cartridge while the PLC rack is powered on?

  No. You must turn off all electrical power to the PLC rack before inserting or removing the 1785-MR cartridge. Handling the module while the backplane is energized risks causing static discharge or electronic component damage.

• What is the difference between the 1785-MR and the 1785-MJ modules?

  The 1785-MR contains 4K words of volatile RAM for fast execution and active editing, whereas the 1785-MJ provides 8K words of non-volatile EEPROM memory for permanent, battery-free backup storage.

• How do I configure the write-protection jumper?

  The module features physical pins on its circuit board. Moving the shorting jumper across the specific pins activates or deactivates the write-protection function. Always configure this jumper before inserting the module into the processor slot.