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RL78 is a 16-bit CPU core by Renesas Electronics with a CISC architecture for embedded microcontrollers developed and manufactured by Renesas Electronics and introduced in 2011.


Renesas Electronics is a developer and manufacturer of semiconductor devices, especially microcontrollers, microprocessors, Power MOSFET, IGBTs, optocouplers, SRAMs and SOC devices.


The RL78 was the first new MCU to emerge from the new Renesas Electronics company from the merger of NEC Electronics and Renesas Technology and incorporated the features of the NEC K0R and Renesas Technology R8C microcontrollers.[1]. The RL78 core variants include the S1, S2, and S3 type cores which evolved from the NEC 78K0R core. The basic S1 core support 74 instructions, the S2 core adds register banking and supports 75 instructions, while the S3 core adds an on-chip multiplier / divider / multiple-accumulate and supports 81 instructions.

The RL78 was developed to address extremely low power but highly integrated microcontroller applications, to this end the core offered a novel low power mode of operation called “snooze mode” where the ADC or serial interface can be programmed to meet specific conditions to wake the device from the extreme low power STOP mode of 0.52uA.



The RL78 family became available with a range of devices from a 20pin 16KB flash memory to 128pin 512KB of flash memory. This RL78/G13 microcontroller family included a +/- 1% on-chip oscillator, watch dog timer, RTC, power-on reset, low voltage detection, 26 channels of 10bit ADC, 16x16 Multiplier, 32/32 Divider, I2C, CSI/SPI, UART, LIN, multi-function timer array and also built-in IEC 60730 safety support in hardware. This combination of elements enables the system designer to achieve high performance (41DMIPS) systems operating at very low power levels and at low cost due to the high level of integration in the microcontroller.


A smaller version of the RL78/G13 was introduced in 2012, the RL78/G12. Introduced with 20, 24, and 30-pin packages with 2 KB to 16 KB small size flash memory although providing the G13 functionality with integrated +/- 1% 24 MHz oscillator, reset circuit, a low voltage detection circuit, watchdog timer, data flash with background operation, and including functional safety, on-chip with A/D converter testing function.

This small device is designated for use as a sub-microcontroller suitable for use as in small home appliances and general consumer electronic devices.


In 2012 an addition to the RL78 family was introduced called the G14. This device offers higher levels of integration with the inclusion of additional multiply and divide and multiply-accumulate instructions capable of faster processing than the RL78/G13, 2 Channel 8-bit D/A, 2 Channel comparator, and timer array making it suitable for motor control applications.

Multi-function Timer Array Unit (TAU):

Timer array with encoder function

Timer array unit (16-bit, 8 ch)

Interval timer (12 bit, 1 ch)

Watchdog timer (17-bit, 1 ch)

Full real time calendar function

Motor control timer (16-bit, 8 ch)

Phase timer (16-bit, 2 ch)

I/O timer (16-bit, 1 ch)


An application specific version (ASSP) of the RL78 core was introduced in 2012 for controlling lighting systems, this device was named the RL78/I1A. Specific features of the device such as special PWM timers enable fine dimming, lighting sequence and colour temperature control with power factor correction of the power supply. In addition integrated communication functions for DALI, DMX512 and multiple sensor & user interface controls are provided. Applications for the RL78/I1A include: building automation, LED drivers, lighting controls, fluorescent ballasts, emergency lighting, HID ballasts, digital power supplies, low-cost inverter controls.


Microcontroller series with LCD Drive

Entering mass production at the beginning of 2013, the RL78/L12 includes integrated LCD drive capability for 35 segments x 8 or 39 segments x 4. Three alternative LCD drive methods mat be enabled: split capacitor, capacitive charge pump or external split resistor. With the split capacitor method a low power LCD drive of 0.6uA at 3V can be achieved. Selectable functions (Seg or I/O) for every segment pin, and drive for both glass and panel.


Automotive Microcontrollers

The RL78 F12, F13, F14, & F15 devices replaced the original NEC 78K0R/Fx3 devices with many updates including faster core speed (32MHz), improved on-chip debug capability, new peripherals, and expanded package and memory options.

Software and Development tools[edit]

The RL78 family is supported with a range of Hardware and software development tools including the GNU Compiler Collection, Renesas CS+ Tools, and IAR Systems compilers with an integrated design environment called Eclipse Embedded Studio or e2studio, CMX, Micrium, Segger, FreeRTOS and Chibios/RT real-time operating systems can be supported. The Renesas CS+ IDE is free for debug-only use and supports standard ELF executable files.

Renesas provides a free code generation tool APPLIcation LEading Tool (Applilet) for the RL78.


The RL78 microcontroller is suited to White Goods (washers, dryers, dishwashers, refrigerators), Small Appliances (power tools, vacuum cleaners, coffee machines), Consumer Electronics, Medical (tooth brushes, blood glucose meters, ECG sensors), to Factory Automation (sensors, gauges, actuators) and Smart Energy (metering, energy control, lighting).

See also[edit]

Hands-on Review of the Renesas RL78/G13 Demonstration Kit


  1. ^ Renesas RL78

External links[edit]