RL78 microcontrollers for simple communication functions, such as low power consumption operation
and measurement of temperature and humidity

Seamless real-time communication is a core prerequisite for all Industry 4.0/IIoT (Industry Internet of Things) implementations and is necessary in order to support serial communication to end devices such as sensors. The RL78 microcontrollers deliver the highest level of low power consumption in the industry and are ideal for end devices with simple functions such as I/O control and temperature and humidity measurement. For the RL78 microcontrollers, Renesas offers Modbus ASCII/RTU and IO-Link solutions that are expected to be widely used in such end devices. And, Renesas offers a PMBus® solution for power management.

Pyramid Diagram of Main Communication Standards of End Device Suitable for RL78


Modbus is widely used in the field of factory automation and plant automation because the specifications are open to the public, free to use, and relatively easy to implement. As a result, it is the most popular serial communication protocol for connecting industrial equipment.

The RS-485 standard is often used in the physical layer of Modbus ASCII/RTU; it is easy to create slave devices that communicate with Modbus ASCII/RTU by connecting an RL78 microcontroller and a Renesas RS-485 transceiver using UART. The RL78 microcontrollers are particularly suitable for simple functions such as low power consumption operation and I/O control, temperature and humidity measurement. Applications like the following are available. Renesas provides application notes and sample software.

You can select an RL78 microcontroller tailored to the application.


IO-Link is a point-to-point serial communication protocol standard used to communicate with sensors and/or actuators. It allows users to control and exchange three types of data-process data, service data, and events. In addition, IO-Link has adopted the M12 connector in the IEC 61131-9 standard. Therefore, simply connect the M12 connector to connect the signal and power and IO-Link can start communication.

The industry-leading RL78 microcontrollers and ZIOL2401 IO-Link interface comprise a complete solution that supports industrial automation areas such as Industry 4.0, Made-In-China 2025 and the Industrial Internet of Things (IIoT). Applications can include pressure sensing, level sensing, weight sensing, and a variety of other sensing functions. Applications like the following are available, and protocol processing can take advantage of the software stack that is supplied by the software vendor.

You can select an RL78 microcontroller tailored to the application.

Software Stack

Each software vendor supports the combined operation of the RL78 microcontroller (MCU) and ZIOL2401 IO-Link PHY. Please contact the software vendor directly for specific details on each software stack.


PMBus is an open standard serial interface for power management and is implemented based on the SMBus serial interface (using the IIC bus). It can make communicating easy between each power supply unit by defining the necessary command language. It can connect and control many power supply units on the bus line.


Software title Software type Type Date Date
ZIP 6.53 MB 日本語
Application: Industrial, IoT Applications
Compiler: CC-RL Function: Communication Interface IDE: e2 studio
Sample Code
ZIP 3.09 MB
Application: Industrial
Compiler: CC-RL Function: Communication Interface IDE: CS+ for CC, e2 studio
Sample Code
ZIP 2.25 MB 日本語 Sample Code
3 items

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RL78 Family Modbus ASCII/RTU Solution

This video will show the steps to connect and operate the RL78 Modbus evaluation environment for master and slave with sample software in the application note.
The evaluation environment uses Renesas' RL78/G22 Fast Prototyping Board and RS-485 Transceivers Evaluation Board.

RL78/G22 Modbus ASCII/RTU Application Note Rev.1.00 (ZIP | English, 日本語)