
Difference Between STC15 MCU and STC51 MCU in Mode 0
The main difference between STC15 MCU and STC51 MCU in mode 0 is that STC15 MCU timer 0 has a 16-bit automatic reload function and can select 1T or 12T mode, while STC51 MCU timer 0 is a basic 13-bit timing/counting function, without automatic reload and usually runs in 12T mode.
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The difference between STC15 MCU and STC51 MCU in mode 0 can be discussed in depth from multiple dimensions. The following is an introduction to the main differences between the two in mode 0 by IOT Cloud Platform.
Overview
STC15 MCU and STC51 MCU are both microcontroller products launched by STCmicro, which differ in function, performance and application scenarios.
The STC51 microcontroller is an improvement based on the traditional 8051 core, while the STC15 microcontroller uses a more advanced core and technology. In the specific context of mode 0, the differences between the two are mainly reflected in the timer function, operating speed, IO port mode and compatibility.
Timer function
1. STC51 microcontroller
- In mode 0, the timer function of the STC51 microcontroller is relatively traditional and mainly follows the timer working mode of the 8051 core.
- Timer 0 is a 13-bit timer in mode 0, consisting of TH0 (high 8 bits) and TL0 (low 5 bits). When overflowing, it enters an interrupt or produces a specific timing effect.
- The counting rate of the timer is related to the crystal oscillator frequency. Usually, the counter is increased by 1 every machine cycle (i.e. 12 clock cycles).

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2. STC15 microcontroller
- The STC15 microcontroller has enhanced and optimized the timer function.
- Timer 0 also supports 16-bit auto-reload function in mode 0, which means that when the timer overflows, the preset value can be automatically reloaded into the timer register, so that continuous timing operation can be achieved without software intervention.
- The STC15 MCU also provides two counting rate options: 12T mode and 1T mode. In 12T mode, the counting rate is the same as that of the STC51 MCU; while in 1T mode, the counter increases by 1 per clock cycle, which is 12 times faster than the traditional 8051 MCU. This feature gives the STC15 MCU a significant advantage in situations where high-speed timing operations are required.

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3. STC51 MCU and STC15 MCU Company
STCmicro is a company that specializes in the design and manufacture of microcontrollers (MCUs) and other semiconductor products. STCmicro’s product line includes various types of MCUs, memories and other electronic components, which are widely used in industrial control, consumer electronics, automotive electronics and other fields.
4. Main products of STCmicro microcontroller
STCmicro’s main products include:
STC8S003 chip: stronger performance, lower price, pin compatible with STM8S003 series12.
STC25Q40 series wide voltage SPI NOR FLASH chip: suitable for wide voltage environment (1.6V~3.60V)12.
15W series enhanced 1T 8051 microcontroller: wide voltage, dual serial port12.
STC12C5A60S2 microcontroller: 80C51 CPU based on high-performance 1T architecture, with 10-bit ADC, two UARTs, on-chip crystal oscillator and other features1.
STC15F104W microcontroller: 4K bytes flash ROM and on-chip high-precision RC oscillator1.
Running speed
1. STC51 MCU
- The STC51 MCU is based on the traditional 8051 core, and its running speed is limited by the core architecture and clock frequency.
- At standard clock frequencies (such as 12MHz), the instruction execution speed of the STC51 MCU is relatively slow, and each instruction cycle requires multiple clock cycles.
2. STC15 MCU
- The STC15 MCU uses a more advanced core architecture and technology, which significantly improves its running speed.
- Especially in 1T mode, the running speed of the STC15 MCU can reach 8 to 12 times that of the STC51 MCU. This feature enables the STC15 MCU to have better performance in situations where high-speed data processing is required.

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IO port mode
1. STC51 MCU
- The STC51 MCU provides a variety of IO port modes to meet the needs of different application scenarios. These modes include quasi-bidirectional IO port mode, push-pull output mode, high-impedance input mode, and open-drain output mode.
- Quasi-bidirectional IO port mode is suitable for situations where bidirectional data transmission is required; push-pull output mode is suitable for situations where greater driving capability is required; high-impedance input mode is suitable for situations where external signals need to be read; and open-drain output mode is suitable for situations where level matching with other circuits is required.
2. STC15 MCU
- STC15 MCU also provides a wealth of choices in IO port mode.
- Compared with STC51 MCU, STC15 MCU may be further optimized and enhanced in IO port configuration and flexibility. For example, STC15 MCU may support more IO port multiplexing functions, higher driving capability, and more flexible input and output configuration.
Compatibility and feature enhancements
1. STC51 MCU
- STC51 MCU has high compatibility with traditional 8051 MCU in hardware and software. This allows developers to easily use existing 8051 development resources and experience to develop applications for STC51 microcontrollers.
- At the same time, the STC51 microcontroller has made some feature enhancements while maintaining compatibility. For example, Flash memory is used instead of ROM, so that the program memory content can be rewritten multiple times; the clock circuit is enhanced, etc.

Difference Between STC15 MCU and STC51 MCU in Mode 0
2. STC15 microcontroller
- The STC15 microcontroller has made more feature enhancements and optimizations while maintaining compatibility with traditional 8051 microcontrollers.
- In addition to the improvements in timer functions, operating speed and IO port modes mentioned above, the STC15 microcontroller may also support more peripheral interfaces (such as SPI, I2C, UART, etc.), higher operating frequencies and lower power consumption.
- In addition, the STC15 microcontroller may also provide richer interrupt resources and more flexible programming models to meet the needs of different application scenarios.
Application scenarios and selection suggestions
1. Application scenarios
- The STC51 microcontroller is suitable for traditional embedded system applications that do not require high operating speed. For example, simple LED control, key scanning, digital tube display, etc.
- STC15 microcontroller is more suitable for application scenarios that require high-speed data processing and complex peripheral interfaces. For example, motor control, wireless communication, audio processing, etc.
2. Selection suggestions
- When choosing STC15 microcontroller or STC51 microcontroller, developers need to weigh the specific application scenarios and needs. If the application has high requirements for running speed and peripheral interfaces, it is recommended to choose STC15 microcontroller; if the application has high requirements for cost and compatibility, you can choose STC51 microcontroller.
- At the same time, developers also need to consider factors such as development environment, development tools and technical support. Both STC15 microcontroller and STC51 microcontroller provide rich development resources and support, but the specific choice still needs to be made according to their own development experience and needs.

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Summary and Outlook
The differences between STC15 microcontroller and STC51 microcontroller in mode 0 are mainly reflected in timer function, running speed, IO port mode and compatibility.
With the continuous advancement of technology and the changing application needs, microcontroller products are also constantly updated and upgraded. In the future, we can expect STC microcontrollers to make greater breakthroughs and progress in performance, power consumption, integration and ease of use.
At the same time, developers also need to continue to learn and master new technologies and tools to adapt to the changing market needs and challenges.
If you want to know about STCmicro Microcontroller (MCU) Company, you can check relevant information on the IOT Cloud Platform website.
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FAQs
STC15 is developed by Hongjing Technology (STC).
STC15 microcontroller is a microcontroller based on enhanced 8051 core launched by Hongjing Technology (STC). It has the characteristics of high performance, wide voltage, low power consumption, super anti-interference, super encryption, etc. It has built-in ADC/PWM/DAC/EEPROM/comparator, etc., which truly realizes the goal of a chip as a system on chip, and integrates a variety of peripherals and functions.
STC51 microcontroller is an enhanced microcontroller based on the classic 8051 architecture, produced by STC. It retains the basic instruction set and architecture of 8051. It has the characteristics of high performance and low power consumption, and enhances the performance and functional expansion. It is widely used in industrial control, automotive electronics, household appliances and other fields.
STC15 MCU in mode 0 (here it is assumed to refer to the working mode 0 of its timer 0) is usually a 16-bit timer mode with automatic reload function. In this mode, the timer can generate a timer interrupt, and the count value can be read from the relevant register, which is suitable for basic timing functions.
STC51 MCU in mode 0 (referring to the working mode 0 of its TIMER 0) is a basic timing/counting function, which is only used as a 16-bit timer. It can generate a timer interrupt,
Compared with STC51 MCU, STC15 MCU has higher operating speed (such as 1T mode), more built-in peripherals (such as ADC, PWM, etc.), stronger anti-interference ability and lower power consumption. At the same time, STC15 MCU may also have some optimizations and improvements in instruction set and programming model.
When choosing between an STC15 or STC51 microcontroller, the specific requirements of the project should be considered, such as operating speed, power requirements, peripheral requirements, cost budget, and support for the development environment and tools. The STC15 microcontroller is more suitable for high-performance, complex-function applications, while the STC51 microcontroller is suitable for cost-sensitive, basic-function applications.
The STC15 microcontroller has an auto-reload function in timer mode 0, which provides more convenient timing operations. The STC51 microcontroller is a 13-bit timer/counter in mode 0, which needs to be selected by setting the TMOD register and has no auto-reload function.
In 1T mode, the running speed of the STC15 microcontroller can be 8 to 12 times faster than the traditional STC51 microcontroller. This is because the STC15 microcontroller has been optimized in hardware design, which improves the clock frequency and instruction execution efficiency.
The STC51 microcontroller has designed four IO port modes: quasi-bidirectional IO port mode, push-pull output mode, high-impedance input mode, and open-drain output mode. These modes provide more flexible IO port usage. The STC15 microcontroller may have more optimization or expansion in IO port mode, but the specific differences need to be consulted in the data sheet of the specific model. However, as far as mode 0 is concerned, there is no direct correlation or significant difference between the two in IO port mode.
The STC15 microcontroller and the STC51 microcontroller are basically consistent in terms of compatibility, and are both compatible with the 8051 instruction set. However, different models of STC microcontrollers may have different hardware characteristics, such as clock frequency, memory capacity, peripheral interface, etc. Therefore, it is necessary to consider specific needs when selecting and using.
In addition to the differences in timer functions, operating speeds, and IO port modes mentioned above, there may be other subtle differences between the STC15 MCU and the STC51 MCU in mode 0. For example, there may be differences in interrupt handling, power management, reset circuits, etc. These differences usually require consulting the data sheet or technical documentation of the specific model to understand clearly.