Schneider Electric PC-0984-380 Modicon 984 Compact Controller Module

The Schneider Electric PC-0984-380 (also identified as Modicon Model 380 or 984-380 ) is an integrated central processing unit (CPU) and power supply module belonging to the Modicon 984 programmable logic controller family. Designed to mount into standard Modicon 800 series housings, this compact module combines 16-bit logic processing with built-in system power, providing a cost-effective automation solution for mid-range industrial control applications. 

The module executes user programs created with the Modicon 984 instruction set at a nominal processing speed of 5 ms per 1, 000 logic nodes. Integrated RAM provides 6K words for user logic and 1, 920 registers for state storage, yielding a total memory capacity of 8K words. Memory retention during line power interruptions is sustained by a 3 V lithium backup battery with a one-year service life, supported by a front-panel LED indicator that provides a 14-day advance warning before memory loss occurs.

A dual-input power supply section allows primary line operation at 115 VAC or 230 VAC (selectable via a slide switch) alongside a dedicated 24 VDC backup or direct primary input. Operating status and diagnostic results are presented via front-panel status LEDs (PWR OK, READY, RUN, and BAT LOW). Physical security is maintained via a key switch on the front panel, which locks out unauthorized access to program logic. 

Functional Specifications

Diagnostics and Power Configuration

The PC-0984-380 incorporates standard Modicon status indicators to assist maintenance personnel during startup and troubleshooting:

• PWR OK (Green): Indicates primary input voltage and internal DC outputs are within tolerance.
• READY (Amber): Lit when the controller successfully passes internal power-up self-diagnostics. 
• RUN (Green): Signals that the CPU is executing user logic.
• BAT LOW (Red): Illuminates when the lithium battery voltage drops below the threshold, providing a 14-day window for battery replacement before user RAM data is degraded. 

Input power wiring accepts standard line AC or 24 VDC auxiliary power. When configuring AC power, ensure the voltage selection slide switch matches the incoming line potential (115 VAC or 230 VAC) prior to applying supply voltage.

Installation Guidelines

Allow a minimum clearance of 12 inches on the left side of the housing for access to power supply connections. Provide at least 6 inches of clearance above and below the module for natural convection thermal management in vertical rack configurations. 

Frequently Asked Questions

Q: What is the main difference between Model 380 and Model 381 in the Modicon 984 series? A: The PC-0984-380 provides standard CPU logic solver and power supply functions, whereas Model 381 includes an onboard real-time time-of-day clock for time-stamped control tasks.

Q: How long will memory be maintained after the red BAT LOW light turns on? A: The onboard lithium battery retains user program logic and state RAM data for up to 14 days after the BAT LOW indicator first illuminates under normal ambient conditions.