ⓘ RL78 Family is a 16- and 8-bit CPU core for embedded microcontrollers of Renesas Electronics introduced in 2010. The basis of RL78 Family is an accumulator-base ..


ⓘ RL78

RL78 Family is a 16- and 8-bit CPU core for embedded microcontrollers of Renesas Electronics introduced in 2010. The basis of RL78 Family is an accumulator-based register-bank CISC architecture with 3-stage instruction pipelining. It has 20-bit 1M Byte address space.


1. Microarchitectures

RL78 Family is an accumulator-based register-bank CISC architecture with 3-stage instruction pipelining. It has 20-bit 1M Byte address space. Its basic instruction set architecture is succeeded from 78K0R, which has 75 same instructions out of 80.

RL78 has three microarchitecture variants as follows.


2. Applications

RL78 covers wide range of application area for mechanical system controls and for user interfaces.


RL78 Family is divided into some groups, those have unique naming rules.

  • L1x: For segment LCD controls
  • I1x: Mainly for industrial use
  • F1x: For automotive use
  • D1x: Specially designed for automotive customers only
  • G1x: For general purpose use

Application examples

RL78 is suitable for consumer electronics, such as major appliances, small appliances, and medical devices. It is also used for factory automation infrastructure, and energy conservation.

For automotive industry, low-power and size constrained applications are ideally suited to RL78s automotive dedicated communication interfaces, such as CAN, LIN, and IEBus, and brushless DC electric motor solutions. Three special grade of maximum ambient temperature, 105 °C 221 °F, 125 °C 257 °F, and 150 °C 302 °F, are available for some products.


3. History

RL78 130nm MF3 flash process 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 78K0R 150nm MF2 flash process and Renesas Technology R8C microcontrollers. 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.


4. Software and development tools

RL78 Family is supported with a various range of hardware and software development tools.

Code generating tools

Renesas provides a free code generating tool named APPLIcation LEading Tool Applilet.


4.1. Software and development tools Compilers and IDEs

The GNU Compiler Collection, Renesas CS+ formerly CubeSuite+, Renesas e 2 studio based on Eclipse, and IAR Systems compiler and development environment are available. The Renesas CS+ IDE is free for debug-only use and supports standard ELF executable files. The RL78 ABI defined by Renesas is compatible with IARs V2 and higher compilers.


4.2. Software and development tools Real-time operating systems

Regarding real-time operating systems, CMX Systems, Inc.s CMX-RTX, Micrium, Inc.s μC/OS-II and MicroC/OS-III, ITRON OS Segger Microcontroller Systems embOS, FreeRTOS, and ChibiOS/RT are supported.


4.3. Software and development tools Code generating tools

Renesas provides a free code generating tool named APPLIcation LEading Tool Applilet.


4.4. Software and development tools In-circuit emulators

Several companies provide on-chip debuggers and full-spec in-circuit emulators. Renesas makes on-chip debuggers as well as third-parties, such as Lauterbach and iSystems. Renesas and iSystems supply full-spec in-circuit emulators.


4.5. Software and development tools On-chip device programming tools

Device programming can be achieved by using the on-chip debug port or by using the special serial programming mode of the devices. Renesas supports the serial programming mode with debug tools via the Renesas Flash Programmer RFP and the stand-alone programmers; PG-FP5 and PG-FP6, while several third-parties support RL78 with their own device programmers.


5.1. Variants RL78/G13

RL78/G13 integrates a +/- 1% accuracy 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.


5.2. Variants RL78/G12

G12 is a smaller version of G13 introduced in 2012. 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.


5.3. Variants RL78/G14

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.

  • Motor control timer 16-bit, 8 ch
  • Multi-function Timer Array Unit TAU
  • Interval timer 12 bit, 1 ch
  • Full real time calendar function
  • Phase timer 16-bit, 2 ch
  • Timer array with encoder function
  • Timer array unit 16-bit, 8 ch
  • Watchdog timer 17-bit, 1 ch
  • I/O timer 16-bit, 1 ch


5.4. Variants RL78/I1A

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.


5.5. Variants RL78/L12

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.


5.6. Variants RL78/F1x

Automotive Microcontrollers

The RL78 F12, F13, F14, & F15 devices replaced the original NEC 78K0R/Fx3 devices with many updates including die shrink, faster core speed 32MHz, improved on-chip debug capability, new peripherals, safety features, and expanded package and memory options. The application note r01an2639ej can be used as a guide when migrating from 78K0R/Fx3 to RL78/F1x.

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