1785-MJ | Allen-Bradley | 8K EEPROM Memory Module

Description

The Allen-Bradley 1785-MJ is an 8K-word EEPROM memory module designed for use with PLC-2 and PLC-5 family processors. It enables reliable program storage and retention without requiring battery backup, ensuring data integrity even during power loss. Built with a removable jumper for write protection, this module is ideal for maintaining critical control logic in demanding industrial automation environments.

Technical Specifications

• Manufacturer: Allen-Bradley

• Model Number: 1785-MJ

• Product Type: EEPROM Memory Module

• Memory Capacity: 8K words

• Compatible Processors: 1772-LW, 1772-LWP, 1785-LT, 1785-LT2, 1785-LT3, 1785-LT4

• Write Protection: Enabled via removable jumper

• RIUP Capability: Not supported (module must be installed/deinstalled with power off)

• Operating Temperature: 0 to 60°C (32 to 140°F)

• Storage Temperature: -40 to 85°C (-40 to 185°F)

• Relative Humidity: 5–95% non-condensing

• Dimensions: 55.4 × 43.9 × 17.4 mm (2.18 × 1.73 × 0.69 in)

• Weight: 0.03 kg (0.06 lb)

• Backplane Requirement: 5 VDC from system power budget

Application Scenarios

The 1785-MJ module is suited for PLC-based systems where permanent program retention is critical. Typical use cases include:

• Factory automation and process control systems

• Power generation and distribution control

• Batch processing systems requiring reliable restart capability

• Legacy PLC-2 and PLC-5 system maintenance or upgrades

Comparison with Similar Models

• 1785-MJ: 8K EEPROM module for PLC-5 processors

• 1785-ME16: 16K EPROM variant offering expanded capacity

• 1785-MJ2: Newer EEPROM model with higher storage and improved access time

FAQs

Q1: Does the 1785-MJ retain data without external power?
A1: Yes, as an EEPROM device, it maintains stored data even when power is removed.

Q2: Can this module be written to directly from the PLC processor?
A2: Yes, programming can be transferred from the PLC memory to the EEPROM using standard write procedures.

Q3: Is the 1785-MJ backward compatible with older PLC-2 processors?
A3: It is compatible with select PLC-2 and PLC-5 processor models listed in the specifications.