R9A02G021 is the first microcontroller with Renesas 32-bit RISC-V CPU core design

Renesas R9A02G021 is the first MCU group to use the company’s in-house designed 32-bit RISC-V CPU core with 3.27 CoreMark/MHz, RV32I base plus M/A/C/B extensions, and features such as a stack monitor register, a dynamic branch prediction unit, and a JTAG debug interface.

Renesas has been making RISC-V chips at least since 2022 with the likes of RZ/Five 64-bit microprocessor and R9A06G150 32-bit voice control ASSP. All those were based on Andes RISC-V cores, but since the company has now designed its own 32-bit core, future Renesas 32-bit RISC-V microcontrollers are all likely to feature the in-house core, starting with the R9A02G021 general-purpose MCU group.

Renesas R9A02G021 RISC-V MCU

Renesas R9A02G021 key features and specifications:

  • RISC-V Core
    • Renesas RISC-V instruction-set architecture (RV32I + MACB + Ziscr, Control and Status Register (CSR) instructions + RISC-V Zifencei Instruction-Fetch Fence)
    • Maximum operating frequency –  48 MHz
    • Debug and Trace – RISC-V External Debug Support
    • cJTAG Debug Port
  • Memory & storage
    • 16 KB SRAM (12KB SRAM and 4KB ECC SRAM)
    • 128 KB code flash memory
    • 4 KB data flash
    • 128-bit unique ID
  • I/Os and peripherals
    • Up to 42 pins for general I/O ports; open drain, input pull-up
    • 6-channel Serial Array Unit (SAU)  – 6x simplified SPI, 3x UART, 6x simplified I2C
    • 2x I2C, 2x UART
    • Remote Control Signal Receiver (REMC)
    • Analog
      • 12-bit A/D Converter (ADC12)
      • 2x comparators (CMP)
      • 2x 8-bit D/A converters (DAC8)
      • Temperature Sensor (TSN)
    • Timers
      • Watchdog Timer (WDT)
      • Realtime Clock (RTC)
      • 8-channel Timer Array Unit (TAU)
      • 32-bit Interval Timer (TML32)
  • Clock Sources
    • External clock input (EXTAL)  – 1 to 20 MHz
    • Sub-clock oscillator (SOSC) – 32.768 kHz
    • High-speed on-chip oscillator (HOCO) – 24/32/48 MHz
    • Middle-speed on-chip oscillator (MOCO) – 8 MHz
    • Low-speed on-chip oscillator (LOCO) – 32.768 kHz
    • Clock trim function for HOCO/MOCO/LOCO
    • IWDT-dedicated on-chip oscillator (15 kHz)
    • Clock out support
  • Safety
    • SRAM parity and ECC error check
    • Flash area protection
    • ADC test function
    • Clock Frequency Accuracy Measurement Circuit (CAC)
    • Cyclic Redundancy Check (CRC) calculator
    • Data Operation Circuit (DOC)
    • Independent Watchdog Timer (IWDT)
    • GPIO readback level detection
    • Register write protection
    • Illegal memory access detection
    • True Random Number Generator (TRNG)
  • System and Power Management
    • Operating Voltage – VCC: 1.6 to 5.5V
    • Low power modes
    • Event Link Controller (ELC)
    • Data Transfer Controller (DTC)
    • Key Interrupt Function (KINT)
    • Power-on reset
    • Low Voltage Detection (LVD) with voltage settings
    • Power Consumption: 162µA/MHz (Active power), 0.3µA (SW Standby), 4µs (Standby wakeup)
  • Packages
    • 48-pin HWQFN (7 mm × 7 mm, 0.5 mm pitch)
    • 32-pin HWQFN (5 mm × 5 mm, 0.5 mm pitch)
    • 24-pin HWQFN (4 mm × 4 mm, 0.5 mm pitch)
    • 16-pin WLCSP (1.99 mm × 1.99 mm, 0.4 mm pitch)
  • Temperature Range – -40°C to +125°C
Renesas FPB-R9A02G021 RISC-V MCU Fast Prototyping Board
FPB-R9A02G021 RISC-V MCU Fast Prototyping Board with Arduino headers

Four devices are currently available with different packages from 16-pin WLCSP up to 48-pin HWQFN. Renesas says the new R9A02G021 MCUs are fully supported by the e² Studio Integrated Development Environment (IDE) just like other microcontrollers from the company with a code configurator, an LLVM toolchain, and the fast prototyping board (FPB) pictured above. But third-party tools and debuggers are also supported including IAR Embedded Workbench IDE with the I-jet debug probe and SEGGER Embedded Studio IDE with J-Link debug probes and Flasher production programmers. Documentation includes the FPB user manual, a Getting Started guide, schematics, Bill of Materials (BOM), and Gerber files.

The R9A02G021 group MCUs have no application-specific features like a machine learning accelerator or graphics engine and are designed as general-purpose devices for IoT sensors, consumer electronics, medical devices, small appliances, and industrial systems.  To demonstrate its functionality, Renesas developed a smart pressure cooker reference design as part of its “Winning Combinations”.

Renesas RISC-V pressure cooker
Block diagram for a smart pressure cooker based on R9A02G021 and other Renesas chips

When I first read the news, I thought IP vendors such as Arm or Andes would have a tough time in the future, as large silicon vendors will develop their own RISC-V cores and related IP, while smaller companies may leverage the existing RISC-V open-source core. So within a few years, the majority of microcontrollers could be RISC-V-based, while RISC-V application processors would ramp up later due to the larger software ecosystem that requires more work. My idea was that maybe in five years RISC-V MCUs would dominate, and RISC-V applications processors in 10 years with a company such as Arm likely to suffer unless they can reinvent themselves.

But I may have been overly optimistic with regards to the timing of RISC-V adoption, as Renesas’ press release quotes “The Microcontroller Market Monitor, 2024 Q1 Edition, Yole Intelligence” with their analyst expecting that “RISC-V should approach 10% of the overall MCU market by the end of 2029 with significant growth potential beyond”.

Some of the Renesas R9A02G021 microcontrollers are available now, with for example, the R9A02G0214CNK (24-pin package) going for $1.27 per unit in 4.9K orders. The Fast Prototyping Board can also be purchased now for $17.29. More details may be found on the product page.

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1 Comment
3 months ago

Companies will adopt RISC-V where there’s good reason to do so : economics, performance/efficiency, availability and geopolitics.

It’s also encouraging to see silicon design companies eager to use the ISA, and companies like ESP promising pin-for-pin replacement silicon, making adoption easy.

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