Allen-Bradley 1785-ME32 PLC-5 Memory Module

Allen-Bradley 1785-ME32 PLC-5 Memory Module

Configured for non-volatile program backup and memory retention in PLC-5 system architecture, the Allen-Bradley 1785-ME32 (1785-ME32 EEPROM Memory Device) provides direct physical/electrical execution. The module interfaces directly with standard PLC-5 processor backplane sockets to store program instructions and data tables without requiring continuous battery maintenance. Operating with an onboard capacity of 32K words, the component maintains execution integrity across power cycles via electrical erase and rewrite cycles directly executed within the host processor slot.

Hardware Specifications

Backplane Bus Interfacing and Firmware Compatibility

The 1785-ME32 memory module draws operating current directly from the host processor internal 5 VDC power rail through dedicated socket contact points. During backplane bus communication cycles, the non-volatile memory controller maintains deterministic read/write timings aligned with the processor instruction cycle clock. Firmware flash compatibility across standard PLC-5 processor variants ensures non-volatile data image validation during CPU startup routines. The EEPROM architecture prevents ladder logic memory corruption caused by sustained backplane voltage dips or RAM battery failure modes.

Frequently Asked Questions

Q: Can the 1785-ME32 memory module be installed or removed while the PLC-5 processor is powered?

A: No. Installing or removing the memory module while power is applied to the rack or processor will cause electrical arc damage to the connector contacts and potentially corrupt the non-volatile memory array. Always remove 120/230 VAC or 24 VDC primary power from the chassis power supply before inserting or extracting the module.

Q: How does the processor utilize the 32K word memory during runtime operations?

A: The processor reads the program image from the EEPROM into active SRAM upon system boot when configured via processor DIP switches or programming software. During runtime, ladder execution operates out of fast SRAM, while the 1785-ME32 serves as the persistent offline backup image.

Q: What is the backplane current load impact when adding this module to a PLC-5 CPU?

A: The module imposes a continuous load of 0.17 A at 5 VDC on the processor internal power circuit. This load must be calculated as part of the total 5 VDC power budget allocated to the 1771 chassis power supply.

Field Installation Guidelines

1. De-energize all power sources connected to the 1771 I/O chassis and host PLC-5 processor before touching internal module slots.
2. Wear an ESD grounding wrist strap connected to the industrial enclosure cabinet earth ground point to prevent static discharge to the exposure pins on the EEPROM board.
3. Locate the designated memory socket on the front or side card edge of the PLC-5 processor module.
4. Align the plastic keying guide notches of the 1785-ME32 with the physical guide tabs in the CPU memory socket.
5. Apply firm, balanced thumb pressure until the connector snaps flush into the socket locking tabs.
6. Verify DIP switch configurations on the PLC-5 processor to enable automatic EEPROM load on power-up if automated recovery is required.
7. Re-apply power to the chassis and verify that the CPU processor status LEDs perform standard diagnostic startup sequences without reporting memory parity errors.