Description

Product Overview

EH‑CPU316A is the mid‑range CPU module for Hitachi EH‑150 series modular PLC, built around a 32‑bit RISC processor, serving as core logic controller for medium‑size discrete and process automation systems. With 15.7K‑step user program memory, built‑in real‑time clock and native PID instruction support, it executes ladder logic, handles rack‑based I/O scanning, and manages multi‑port serial communication for HMI, SCADA and remote modem connection.

Many legacy plant retrofit projects face constraints of limited cabinet space and mixed serial instrument devices. EH‑CPU316A addresses these demands with dual onboard serial ports, one switchable RS‑232C / RS‑422 / RS‑485 interface supporting modem dial‑up for remote monitoring. It works cooperatively with digital, analog and optional fieldbus expansion modules (Profibus‑DP, DeviceNet) to build distributed control systems without upgrading to higher‑grade CPU hardware. Status LED indicators deliver runtime, fault and diagnostic feedback, easing on‑site troubleshooting for ageing installed base. It is widely used as drop‑in spare for existing EH‑150 racks in power, water‑treatment and manufacturing sites.

Technical Specifications

Parameter name	Parameter value
Product model	EH‑CPU316A
Manufacturer	Hitachi Industrial Equipment Systems
Product type	EH‑150 Series PLC CPU Module
Processor	32‑bit RISC (Super‑H)
Program capacity	15.7 K steps
Instruction speed	Approx. 1 µs per basic instruction
Backplane	EH‑150 rack backplane
On‑board ports	Port1: RS‑232C / RS‑422 / RS‑485; Port2: RS‑232C, max 38.4 kbps
Built‑in functions	Real‑time clock, PID control, Modem remote monitoring
Max expandable I/O	Up to 704 points total system I/O
Power consumption	400 mA (24 V DC backplane supply)
Operating temperature	0 °C ~ +55 °C
Mounting	Plug‑in onto EH‑150 base rack
Protection class	IP20 (cabinet installation)
Weight	450 g
Certifications	CE, complies with JIS industrial standards

Key Features and Advantages

integrated real‑time clock & PID function: EH‑CPU316A embeds hardware real‑time clock and native PID control instructions. Closed‑loop regulation for temperature, pressure and flow can be implemented without additional special‑purpose modules, reducing hardware cost for process‑oriented applications.

dual serial ports with modem capability: Port 1 supports modem control function, enabling remote monitoring and program maintenance via public telephone lines. This is highly valuable for unattended field‑station sites, without deploying Ethernet hardware.

expandable fieldbus architecture: Supports optional Profibus‑DP master, DeviceNet master modules. One CPU can mount up to two Profibus‑DP master modules, connecting large volumes of distributed remote I/O and field devices.

diagnostic LED status indication: Front‑panel LEDs display RUN, STOP, error and system alarm status. Operators can quickly identify program faults, backplane failure or communication anomalies during routine inspection.

drop‑in spare for legacy systems: Fully plug‑and‑play compatible with existing EH‑150 racks. Program can be directly downloaded from original project; no rack modification required during component replacement for plant outage maintenance.

memory card support: Compatible with EH‑MEMP / EH‑MEMD memory card for program backup, easy program duplication and on‑site fast restore in case of CPU replacement.

HITACHI EH-CPU316A

Application Fields

EH‑CPU316A is widely deployed in EH‑150 automation racks for water‑wastewater treatment plants, power auxiliary control, metallurgy auxiliary equipment, and general machinery manufacturing. In water‑treatment facilities, it executes sequence logic for pumping stations, valve interlocks, dosing control, and PID‑based flow/pressure regulation, communicating with local HMI and central SCADA via serial links.

Within thermal‑power‑plant auxiliary control cubicles, it governs fans, dampers, pump groups and chemical‑water processing systems. The modem remote‑monitoring function supports off‑site diagnosis for unmanned auxiliary substations.

For machinery‑retrofit scenarios, EH‑CPU316A serves as spare replacement for ageing EH‑150 CPUs. It re‑uses existing I/O racks, field wiring and HMI configuration, extending service life of automation assets while controlling modernisation investment. It is also adopted in material‑handling systems and process skids requiring moderate I/O scale and closed‑loop control.

Installation and Maintenance

pre‑installation preparation: Power down the whole EH‑150 rack before inserting EH‑CPU316A. Check backplane connectors for dust and oxidation. Confirm rack power‑supply module output is within rated range. Complete hardware configuration setting inside LADDER EDITOR programming software, download user program and parameter settings before putting into operation. Verify backup battery condition to avoid RTC and retentive‑data loss after power‑off.

maintenance recommendations: Check front‑panel LED status during regular plant inspection. Monitor battery ageing; replace lithium battery periodically to prevent clock and data loss. Back‑up complete program to memory card or PC for spare‑recovery purpose. Do not hot‑swap EH‑CPU316A under energised rack conditions, as this will halt user logic execution. The CPU module contains no field‑serviceable internal parts; send defective units to Hitachi‑authorised repair centres.

Product Warranty & Support

Each EH‑CPU316A passes factory logic testing, backplane interoperability and communication‑port validation before shipment. Standard equivalent warranty covers manufacturing defects for 12 months from delivery date. Spare‑part sourcing, remote technical guidance, program backup‑restore support are available for spare‑replacement, commissioning and site SAT. Application engineers provide support for PID tuning, modem remote‑connection setup and fieldbus configuration. Long‑term spare‑parts inventory mitigates obsolescence risk for installed EH‑150 automation systems.

HITACHI EH-CPU316A EH‑150 Series PLC CPU Module