Allen-Bradley 1785-L30B Standard Processor Module

Configured for central logic processing and multi-channel communication execution in 1771 Universal I/O chassis networks, the Allen-Bradley 1785-L30B (1785-L30B PLC-5/30 Standard Processor Module) provides direct physical execution of discrete and analog control algorithms.

Hardware Specifications

Deterministic Backplane Bus & Communication Architecture

The 1785-L30B module mounts directly into the primary slot of a 1771 Universal I/O chassis, interfacing through the backplane bus to execute real-time I/O updates across up to 1024 digital and analog points. Its dual integrated Data Highway Plus (DH+) and Remote I/O (RIO) channels operate deterministically to support peer-to-peer data exchange and distributed rack monitoring. Onboard battery-backed 32k word SRAM stores application ladder logic and configuration tables, maintaining program state across power cycles through dedicated memory bus lines.

Frequently Asked Questions

Q: What is the backplane current draw for the 1785-L30B processor?

A: The 1785-L30B processor draws 2.3 A at 5 VDC from the 1771 chassis power supply backplane, consuming up to 12 W of total system power dissipation.

Q: How is memory retained during complete chassis power interruptions?

A: Active system programs and registers in the 32k word SRAM are sustained by an onboard 1770-XYC lithium battery assembly. Optional non-volatile EEPROM modules can also be installed for permanent program preservation.

Field Installation Guidelines

1. Power Isolation: Disconnect main power from the 1771 chassis power supply prior to inserting or removing the 1785-L30B module to avoid backplane pin arcing or electrical damage.
2. Module Placement: Align the circuit board with the top and bottom card guides in Slot 0 of the 1771 I/O chassis. Push firmly until the rear connector seats into the backplane, then lock the upper and lower chassis latches.
3. Communication Wiring: Route DH+, Remote I/O, and RS-232 serial cables away from AC power conductors and variable frequency drive wiring. Terminate twinaxial shield wires strictly at a single chassis ground connection point to prevent ground loops.
4. Battery Installation: Verify the 1770-XYC lithium battery harness is properly connected to the processor before placing the system into operation.
5. Keyswitch Configuration: Set the front panel key switch to PROG for initial program downloading via serial or DH+ ports, then switch to RUN or REM for live execution.