Introduction to rl78 MCU of Renesas Electronics

The 16 bit rl78 embedded microcontroller of Renesas electronics integrates advanced low-power technology and excellent performance. This is because it adopts advanced power management system, which can promote the efficient use of power and extend the battery life of portable applications. Rl78 family MCU is very suitable for various application development in multiple target markets, such as home appliances, small appliances, industrial and building automation, home medical diagnostic equipment, personal health care equipment and consumer electronic products. Compared with similar microcontrollers, rl78 MCU has higher energy efficiency and longer battery life, so it provides an ideal platform for IOT sensor system. It can process data and signal closer to the edge of the network, so as to reduce delay and achieve real-time reporting.

Overview of key features of rl78 MCU:

Real low power operation, with power consumption as low as 0.23 in standby stop mode μ A. Three low power consumption modes are provided to achieve the most efficient energy consumption level and maximize the battery life.

High processing performance, rl78 / G14 can provide up to 51.2 DMIPS performance at 32mhz.

Extensive scalability, offering over 1000 devices, 10 to 128 pin packages, and 1 KB to 512 KB flash memory.

The built-in on-chip peripheral function can reduce the total system cost and eliminate the space limitation.

Excellent quality, reliability and safety in accordance with UL / IEC 60730.

Renesas electronics provides a comprehensive ecosystem, including development tools, solution kits, online resources and a network of partners, to help customers minimize design and development costs and accelerate product time to market.

Real low power components that reduce energy consumption

Rl78 family products mainly provide real low power consumption through two ways: reducing the energy consumption of MCU itself; Help to achieve more efficient energy management of terminal system.

The rl78 MCU of Renesas electronics is only 0.23 in the standby stop mode (in the stop mode, there is no clock working and the ram content is reserved) μ A’s ultra-low power consumption, while in the CPU running mode, in running NOP instructions and generating 144 μ At a / MHz working current, it can still reach 66 μ A / MHz low power consumption. As a result, it can provide up to 51.2 DMIP performance at 32 MHz while maintaining high energy efficiency. The performance of rl78 family products is much higher than other 8-bit and 16 bit microcontrollers on the market.

Rl78 MCU has an energy management system, which can further promote the efficient use of power supply, which is crucial to extend the battery life of portable applications. Due to the low power consumption of rl78 MCU, when using + 3V power supply and enabling all peripherals, its power consumption is generally less than 20MW at 32mhz. Therefore, it is easy to meet the standby power requirements of the electrical industry, that is, the power obtained from the AC line is less than 100MW. When working in any low-power mode (snooze, halt and stop), the power consumption of rl78 MCU can be further reduced, and the battery life can be maximized by disabling CPU and unused peripherals.

One of the key factors to maximize the battery life is to ensure that the CPU is idle as much as possible, and has flexibility when it is active, so as to improve the work efficiency as much as possible. In CPU run mode, when the highest performance is not needed, the internal oscillator of rl78 can even expand down to a lower frequency to save the current consumption of MCU. Halt mode pauses CPU processing, but allows all peripherals to run. This mode will keep the running system clock state before entering the halt mode, so that the CPU can quickly resume work without waiting for the system clock to start. Compared with CPU running time, halt mode can save up to 80% of MCU total current. In stop mode, both watchdog timer and voltage detector (such as power on reset (POR) circuit) work while all RAM data is retained, while the system consumes only 0.53 μ A current (typical value). In addition, the 15KHz low-speed clock and 32kHz secondary clock can still operate, supporting the operation of date / time real-time counter, LCD controller driver boost circuit and 8-bit or 12 bit interval timer of timing events. All these low-power peripherals can be used in stop mode with a total current consumption of less than 1 microampere.

Rl78 adds a special low-power mode, called snooze mode, which is not found in previous generations of low-power MCU. Snooze mode allows serial communication and ADC converter to start from stop mode via high-speed internal oscillator clock without timing CPU clock. Therefore, snooze mode is similar to halt mode in that it does not need CPU intervention before data acquisition, thus saving current consumption. This mode is very suitable for battery powered systems because it can significantly improve battery life.

Characteristics and application solutions of rl78 MCU in Renesas Electronics

Figure 1. Rl78 provides three low power operation modes to maximize battery life

Excellent performance supports more data processing at the edge of the network

Rl78 MCU provides unparalleled power performance ratio. Rl78 uses optimized 16 bit CPU and Harvard architecture to provide complete 16 bit data bus for ram, control registers and peripherals. In addition, a three-level pipeline is provided to implement instruction level parallel processing in a single processor. 86% of the instructions can be executed in one or two clock cycles, and the maximum clock speed can reach 32mhz. The test result of this high performance in the Dhrystone benchmark is 1.6 DMIPS / MHz, that is to say, the processing performance at 32 MHz is about 51.2 DMIP. Rl78 family products also provide the largest working voltage range of similar products: 1.6V to 5.5V.

In addition, rl78 MCU provides hardware support for multiplication, product accumulation and division functions. Multiplication and product accumulation are performed in one or two cycles respectively. With up to four independent DMA channels, it can transfer data between RAM memory and peripherals in two clock cycles. However, some rl78 MCU product groups have DTC (data transmission control) function, which can provide higher flexibility and more channels for peripheral data transmission function.

A large number of optional devices provide scalability

The MCU product line provided by Renesas rl78 family products is one of the most extensive MCU product lines in the industry, with more than 1000 devices, 17 different pin numbers from 10 to 128 pins, and 1KB to 512KB flash memory. General purpose MCU is used in G series, while LCD controller driver function is provided in L series. F series can meet the needs of automotive applications. I series can meet the needs of industrial applications, such as lighting, metering or testing. Designers can easily expand from the minimum code flash memory capacity to the maximum code flash memory capacity in the same series of products. They can easily add more I / O and functions by migrating to devices with a larger number of pins, without rewriting the code driver previously written and debugged. The software code can be reused in the whole rl78 family products. For example, any driver software of internal integrated circuit bus (I2C), universal asynchronous receiver / transceiver (UART) or analog-to-digital converter (ADC) running on rl78 MCU with small pin number can be used on devices with large pin number without code change, and even can be used among different rl78 series types. In addition, the I / O port pin and peripheral function pin can be expanded from the minimum pin number to the maximum pin number. At the same time, as the pin number increases, the logical port pin number is maintained, and the physical PCB layout of peripheral pins in the same order position is maintained.

On the other hand, with the help of the peripheral I / O redirection register (pior) function of rl78, the designer can remap the physical pin connection to the selected peripheral to optimize the peripheral pin function. Due to the limitation of layout or peripheral pin sharing, the existing peripheral I / O allocation may conflict. In this case, pior can optimize the peripheral pin function by reducing the function bottleneck on the pin.

Using more powerful MCU to reduce system cost

Rl78 MCU realizes high integration, and has built-in advanced peripherals. By using the following on-chip components, the external components are eliminated, so as to reduce the system cost

High speed system oscillator with frequency accuracy of ± 1%, with calibration register.

· watchdog timer.

Low voltage detection reset circuit.

Data flash memory is used to store user preferences, machine parameters and log data, so no external EEPROM is required. Rl78 data flash supports one million erase / write cycles, matching the life of a typical EEPROM.

Temperature sensor with range from – 40 ℃ to + 85 ℃.

Multi power interface.

Characteristics and application solutions of rl78 MCU in Renesas Electronics

Figure 2. Rl78 MCU integrates more peripheral functions in the chip, which reduces the total cost and the space occupied by components

Built in quality and safety

Rl78 MCU has a variety of security functions, which can ensure the normal operation of devices and enhance the reliability of the system.

Rl78 MCU provides “always on” protection for software code and data stored in flash memory. Rl78 flash memory adopts the verified 130 nm flash cell structure, which can realize the lowest power error correction coding (ECC) and encode 38 bits on each 32-bit flash memory. If the modification status of flash memory exceeds the ECC error correction ability, rl78 CRC (cyclic redundancy check) function module can identify serious errors, so that the software can react immediately and shut down MCU safely.

In addition, rl78 flash supports on-chip debugging (OCD), which provides password protection to prevent hackers from reverse engineering customer application code. However, authorized users who provide the correct password can view the code flash to obtain the revision number, or confirm self programming code changes.

For external rl78 flash programming, three independent flash security bits can be set for different protection strategies

Erasure protection prevents flash programmers from remapping code and reusing hardware.

Write protection prevents the use of backdoor methods to re image a single 1K code block.

The boot cluster protection prevents external chip erase operation from erasing, but it also controls all aspects of boot loader operation according to user code self programming sequence.

Rl78 MCU adopts UL / IEC 60730 certified hardware modules, so they can identify faults and shut down safely. In addition, the software module of rl78 self-test library has been certified by UL and IEC. Customers can quickly implement these UL and IEC requirements in their application systems.

Rl78 MCU can work safely in extreme temperature range from – 40 ℃ to + 105 ℃.

Ecosystem provides abundant resources to help speed up time to market

Renesas electronics provides a complete development support ecosystem designed to help designers deliver systems more quickly and reduce errors. This ecosystem includes:

Hardware tools, such as Renesas electronic promotion board; Renesas electronic entry kit; Iecube is a high performance full specification simulator for rl78 family products; E1 / E2 and EZ cube.

Software tools, such as IAR embedded workbench, which fully supports C and C + +, with Misra C language rule checking tool; The E2 studio ide based on eclipse provides an integrated development environment for Renesas electronic MCU; Appliet code generator; And various real-time operating systems.

Rich online resources, such as Renesas Rulz, an online community where developers can seek peer support; My Renesas, a free online subscription service for document downloads and reminders; Renesas interactive, which provides customized online training courseware.

Characteristics and application solutions of rl78 MCU in Renesas Electronics

Figure 3. Full set of tools to support rapid and efficient development

Brief introduction of rl78 quick solution

Quick solutions are easy to build reference kits that help designers develop products based on rl78 in many of the most popular embedded systems markets. We currently offer 20 fast solutions to help our customers cope with development challenges and opportunities in multiple target application areas, such as home appliances, portable medical and personal healthcare solutions, building and industrial automation and consumer electronics.

Rl78 rapid solution can solve the most challenging design problem for developers when they are trying to quickly prototype new Internet of things and embedded applications. These challenges include configuring wireless features of IOT sensor nodes, or optimizing low-power features to extend the battery life of remote devices.

Rl78 quick solution can be downloaded from Renesas website, including user manual, schematic diagram, bill of materials, source code and project documents, covering all the resources that designers need to complete new product prototype design easily and quickly.

Here is an example of how rl78 intelligent solutions can speed up the design process in popular target markets.

Rl78 rapid solution for designing fine particulate matter 2.5 monitoring devices using portable batteries

The rapid solution design reference provides background documents and source code for the design of low-cost, low-power portable devices, which can measure and detect the concentration of fine particulate matter 2.5 (PM2.5) in real time.

The diameter of PM2.5 particles is less than 2.5 μ m, which is about 3% of the diameter of human hair. The natural sources of PM2.5 particles include sea salt, forest fire, pollen and mold. They are natural and therefore difficult to control and often unregulated. Human sources of PM2.5 particles, such as fuel combustion, industrial combustion process and vehicle emissions, can be regulated. Measuring and monitoring PM2.5 levels is critical in many environments, including industrial automation, construction, and agriculture.

The air quality monitor in the fast solution uses a 48 pin rl78 / L12. Because this MCU includes on-chip LCD controller / driver, the air quality measurement data can be displayed on the easy to read LCD display. The 4-bit LCD panel is driven by 12 lines, including 8 segment lines and 4 common lines. The 48 pin configuration allows optimized design, leaving only four unused MCU pins.

The LCD display can indicate the air quality, and a colorful LED can display the corresponding air quality level. If the preset threshold is exceeded or the battery voltage drops below 2.8V, the buzzer will be activated.

Other important features of rl78 / L12 include I / O port, a / D converter for smoke / particle reading, buzzer, LCD controller, stop mode, and other features suitable for small household appliances. The threshold and PM2.5 concentration data can be saved in the external EEPROM (if the data size is less than 2KB, it can also be saved in the internal data flash of MCU). In addition, the DC-DC Converter IC controls the battery discharge, and the battery charger IC controls the charging, providing very low standby power to maximize the battery charging life. Standby current as low as 0.56 μ A。

Characteristics and application solutions of rl78 MCU in Renesas Electronics

Figure 4. Hardware prototype of PM2.5 monitor using rl78 L12 based on rapid solution


The rl78 family products of Renesas electronics include a large number of general-purpose MCU for users to choose, which can be used as a platform for various application specific designs. Rl78 MCU really realizes low power consumption, and the current consumption in active mode is 66 μ A / MHz to 144 μ A / MHz, standby current is 0.5 μ A to 0.6 μ A. Use low-speed clock and low-power timer to work. They can provide high performance up to 1.6 DMIPS / MHz and 51.2 DMIP at 32 MHz CPU. Rl78 MCU provides a wide range of scalability, including code memory capacity and pin count. It also provides a high degree of on-chip integration to help reduce system costs. They provide advanced hardware security features as well as UL / IEC certified self-test software libraries to meet the UL / IEC 60730 standard. Rich development tool environment, third-party partners and online resources can help system designers quickly and accurately meet the needs of the fast-growing embedded system market.

Another very important resource is the rl78 rapid solution design of Renesas electronics, which can significantly speed up prototype development and provide a downloadable design document library. Fast solutions for some of the most popular embedded devices and the Internet of things market, help designers more quickly and easily build compact energy-efficient systems.

Editor in charge: GT

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