Microcontroller incorporating a 24-bit ΔΣ A/D converter for measuring instruments including smart meters


The RX21A group is the product that 24-bit Delta-sigma ADC is built in for measuring instruments such as a smart meter.
PGA (Programmable Gain Amp) is built in Delta-sigma ADC, which is possible to amplify analog signal at most 64 times.
The RX21A group has peripheral functions with special features, such as RTC which enables Time capture on event-signal input through external pins and DEU (Data Encryption Unit) which enables to use Encryption/decryption functions of the AES standard.


Key Features:

CPU core RX CPU General registers: 32-bit x 16
Multiplier: 32-bit multiplier Divider: Yes
Multiply-accumulator: Yes (two types: memory-to-memory operations and register-to-register operations)
Memory-protection unit (MPU)
Maximum operating frequency 50 MHz
Power supply voltage 1.8 to 3.6 V
Program Flash max. 512 KB
Data Flash 8 KB
SRAM max. 64 KB
On-chip peripheral functions Transfer functions DMA controller (DMACA): 4 channels
Data transfer controller (DTCa)
Timers Multi-function timer pulse unit 2: 16 bits x 6 channels (MTU2a)
Port output enable 2 (POE2a)
8-bit timer (TMR): 8 bits x 2 channels x 2 units
Compare match timer (CMT): 16 bits x 2 channels x 2 units
Watchdog timer (WDTA): 14 bits
Realtime clock (RTCb)
Communication functions Serial communications interface (SCIc): 5 channels (1ch: IrDA x 1channel)
I2C bus interface (RIIC): 100, 80-pin:2 channels; 64-pin: 1 channel
Serial peripheral interface (RSPI): 2 channels
Analog functions 24-bit Delta-sigma A/D converter (DSAD): 100-pin: 7 channels; 80-pin: 4 channels; 64-pin: 3 channels
10-bit A/D converter (AD): 100, 80-pin: 7 channels; 64-pin: 4 channels
10-bit D/A converter (DA): 100, 80-pin: 2 channels; 64-pin: none
ComparatorA (CMPA): 100, 80-pin: 2 channels;, 64-pin: 1 channel
ComparatorB (CMPB): 2 channels
Encryption functions Data Encryption Unit (DEU)
Safety functions Clock Frequency Accuracy Measurement Circuit (CAC)
Data Operation Circuit (DOC)
Independent watchdog timer (IWDTa): 14 bits
Self-diagnosis Function of 10-bit ADC/AD Input Disconnection
Detection CRC Calculator (CRC)
Clock Generation Circuit Main clock oscillator
Sub-clock oscillator
Low-speed on-chip oscillator (LOCO)
High-speed on-chip oscillator (HOCO)
PLL frequency synthesizer
Dedicated on-chip oscillator for the IWDT
Others Event link controller (ELC)
Multifunction Pin Controller (MPC)
Temperature Sensor (TEMPSa)

Power-on reset Circuit (POR)

Voltage Detection Circuit (LVD)
On-chip debugging function Planning
Low power consumption modes 4 modes
Sleep mode
All-module clock stop mode
Software standby mode
Deep software standby mode
Packages PLQP0064KB-A (64-pin LFQFP,10x10mm,0.5mm pitch)
PLQP0080KB-A (80-pin LFQFP,12x12mm,0.5mm pitch)
PLQP0100KB-A (100-pin LFQFP,14x14mm,0.5mm pitch)
PTLG0100JA-A(100-pin TFLGA,7x7mm,0.65mm pitch)

Pin Count / Memory Size Lineup:

Program Flash



Block Diagram:

RX21A Block Diagram

You can find an explanation of orderable part numbers here.

Resources for Software and Hardware

Title Description
My Renesas Create a My Renesas account to use our tool download services, receive e-newsletter/update notifications, and take advantage of our other services.
e-learning Information for studying and learning about microcontrollers and microprocessors.
FAQ Frequently asked questions and useful hints for development.
Forum A forum and community site to share technical information, questions and opinions with others who use Renesas products.


Software Design Support

Title Description
e² studio This integrated development environment (IDE) is based on the popular combination of the open-source Eclipse IDE and its CDT plug-in that enables C/C++ language development.
CS+ This integrated development environment (IDE) can be used for coding, assembly, compiling, and simulation. CS+ is also included with starter kits.
E2 emulator Lite This entry-level on-chip debugging emulator provides functionality equivalent to that of the E1 emulator at a low price.
E2 emulator This on-chip debugging emulator has advanced features that improve the efficiency of development. In addition to the basic functions from debugging to flash programming, this emulator supports hot plug-in and external triggers as standard items. This emulator also helps to reduce development time by downloading at high speeds (compared to the E1 emulator) and the ability to work in combination with various solutions such as the tuning of current drawn by systems under development.
E20 emulator This on-chip debugging emulator has enhanced debugging facilities such as large-capacity tracing and real-time RAM monitoring when used in combination with RX600 and RX700 MCUs (this emulator provides debugging functionality equivalent to that of the E1 emulator for other MCUs).
E1 emulator This on-chip debugging emulator is a standard model which provides basic debugging functions (production is to be discontinued at the end of December 2019).


Hardware Design Support

Title Description
IBIS/BSDL IBIS standard simulation data is required for high-speed board design and can be used to run simulations to examine and troubleshoot issues such as waveform reflection, ringing, and so on, before producing the actual board.

BSDL is a data input format supported by most IEEE 1149.1 (JTAG)-compliant tools. The automatic test pattern generation (ATPG) and automatic test equipment functions of these tools facilitate testing.
Resonator Information Please search for your resonator on its manufacturer's site linked below. If you require optimal oscillation circuit constants for your particular system, please ask the manufacturer of the oscillator.

For Main clock resonator :
KYOCERA: Click here for RX21A oscillation evaluation result.
Murata Manufacturing: For IC Manufacturer, select Renesas Electronics, and enter R5F521A into the IC Part Number search box.

For Sub clock resonator :
KYOCERA: Click here for RX21A oscillation evaluation result.
You can filter the sample codes and application notes that are displayed using the below filters.

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