Renesas R5F121BCMNA#20

Overview

R5F121BCMNA#20 from Renesas Electronics is a 32-bit RL78/G16 microcontroller with 32 KB code flash, 2 KB RAM, and 15-channel capacitive touch sensing unit (CTSU), operating at 2.4–5.5 V supply and rated for −40°C to +125°C industrial use. It integrates 8× 16-bit timers, 10-bit A/D converter (11-channel), real-time clock with calendar, and multiple serial interfaces including UART, simplified SPI (CSI), simplified I²C, and full I²C.

For engineers reviewing the R5F121BCMNA#20 datasheet, R5F121BCMNA#20 pinout, R5F121BCMNA#20 application, or R5F121BCMNA#20 equivalent, key selection considerations include its HWQFN-32 package with 0.5-mm pitch, 32-pin thermal-enhanced layout, support for touch-based HMI in space-constrained industrial controls, and compatibility with Renesas' RL78 development ecosystem including E2 emulator and CS+ IDE.

Technical Context

The R5F121BCMNA#20 implements the RL78 CPU core-a CISC architecture with 3-stage pipeline-enabling instruction execution times from 0.0625 μs (16 MHz high-speed on-chip oscillator) to 30.5 μs (32.768 kHz subsystem clock). It supports HALT and STOP low-power modes, on-chip debug, and self-programming flash without boot swap.

Its peripheral set includes a 99-year RTC with alarm and correction, 12-bit interval timer, watchdog timer, two comparators, and configurable serial interfaces (up to 3 CSI, 3 UART, 3 simplified I²C, and 1 full I²C). The CTSU supports both self-capacitance (15 keys) and mutual-capacitance (16-key matrix) operation.

Key Specifications

Pinout & Package

Package: 32-pin HWQFN (5.0 × 5.0 mm, 0.5-mm pitch) with exposed die pad for thermal dissipation; RoHS-compliant, moisture-sensitive level 3.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microcontroller applications.

Compared with R5F121BCMNA#20, the R5F121BCGNA#20 reduces thermal qualification cost but limits maximum operating temperature by 20°C, while the R5F121BAMNA#20 cuts flash capacity by 50%-a trade-off acceptable only when code size is tightly constrained and no future feature expansion is planned.

Availability

R5F121BCMNA#20 is available at Aetrix Electronics and suitable for industrial motor control, smart appliance HMI, energy metering interfaces, and automotive cabin sensor nodes requiring stable component supply across extended temperature ranges.

Supply support for R5F121BCMNA#20 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Renesas Electronics is a global semiconductor leader specializing in microcontrollers, analog, and power solutions for automotive, industrial, and IoT markets.

The RL78/G16 product line delivers ultra-low-power 32-bit MCUs optimized for cost-sensitive, thermally demanding applications requiring integrated touch, precision timing, and robust serial connectivity.

FAQ

What is the maximum operating frequency and clock source configuration for the R5F121BCMNA#20?

The R5F121BCMNA#20 supports up to 16 MHz operation using its on-chip high-speed oscillator, selectable from 1 MHz, 2 MHz, 4 MHz, 8 MHz, or 16 MHz. Frequency accuracy is ±1.5% over −40°C to +125°C. External crystals (X1/X2) can also drive the main system clock for higher precision, and the subsystem clock runs at 32.768 kHz for RTC and ultra-low-power modes. All clock sources are configurable via system control registers in the R5F121BCMNA#20.

Does the R5F121BCMNA#20 support background data flash rewriting while executing code from main flash?

No, the R5F121BCMNA#20 does not support background operation (BGO) for data flash rewriting. During data flash write/erase operations, instruction execution from code flash memory is halted. This requires careful firmware sequencing-typically entering a safe state, disabling interrupts, and using the flash control peripheral to manage the rewrite sequence before resuming normal operation. The R5F121BCMNA#20 specification explicitly states "BGO is not supported" in its data flash section.

How many capacitive touch channels does the R5F121BCMNA#20 support, and what configurations are available?

The R5F121BCMNA#20 integrates a 15-channel Capacitive Touch Sensing Unit (CTSU) supporting both self-capacitance (up to 15 independent keys) and mutual-capacitance (matrix configuration supporting up to 16 keys using transmit/receive pin combinations). All 15 channels are accessible via dedicated TSCAP pins (e.g., P02, P03, etc.) and configurable through the CTSU control registers. This capability is confirmed in the R5F121BCMNA#20 datasheet Section 1.1 and Table 1-6 pin functions.

What serial communication interfaces are integrated into the R5F121BCMNA#20?

The R5F121BCMNA#20 integrates four serial interface types: up to three simplified SPI (CSI) channels, up to three UART channels, up to three simplified I²C channels, and one full I²C channel (IICA). These are multiplexed across GPIO pins (e.g., P00–P07, P16–P17, P40–P43) and configured via peripheral I/O redirection registers. The R5F121BCMNA#20 supports simultaneous use of multiple interfaces-for example, UART for host communication, CSI for display driver, and IICA for EEPROM access.

Is the R5F121BCMNA#20 pin-compatible with other RL78/G16 variants in the same package?

Yes, all RL78/G16 devices in the HWQFN-32 package-including R5F121BCMNA#20, R5F121BCGNA#20, and R5F121BAMNA#20-share identical pinouts and electrical characteristics. Pin mapping, power/ground locations, and peripheral function assignments (e.g., P00 = TOOLTxD/SO00/TxD0) are fully consistent across M-, G-, and A-grade 32-pin variants. This allows direct substitution based on temperature grade or flash size without PCB redesign, as verified in Tables 1-6 and Figure 1-1 of the R5F121BCMNA#20 datasheet.