After the microcontroller is reset, do some undefined (unused floating pins) pins have any level output? Are they all high level or low level, or high impedance, or no signal?
Keywords：MCU
Reference address：Definition of MCU output pins
I have another question. I want to change the compiler of KEIL 51 programming software. How should I change it?
1. For the traditional 51 MCU, after reset, all ports output 1, that is, high level. For AVR MCU, PORTx=0x00, DDRx=0x00 is in high impedance state, and the same is true for PIC MCU.
2. If you want to control the LED, you should connect it in reverse, that is, the LED will be lit when the port outputs 0. In addition, for the commonly used 51 MCU, the current output of high level is small, while the current absorbed by low level is large. This is what you need to know. Of course, STC's MCU uses a push-pull port, which can withstand a large current when outputting 1 or 0.
3. Of course, after the MCU is reset, the port state is a certain high level (such as 51 MCU) or high impedance (AVR, etc.). It is not wrong to initialize it in the program! Some compilers can automatically generate code (such as the CVAVR compiler of AVR MCU), and they all initialize the port to high impedance at the beginning of the program. If you want to save code space, you can remove these codes.
4. In addition to Keil UV2, IAR for 8051 compiler is also good, but I think IAR's compiler is mainly aimed at enhanced microcontrollers such as C8051F series and CC2430. For ordinary microcontrollers... it seems to be a waste of talent!
2. If you want to control the LED, you should connect it in reverse, that is, the LED will be lit when the port outputs 0. In addition, for the commonly used 51 MCU, the current output of high level is small, while the current absorbed by low level is large. This is what you need to know. Of course, STC's MCU uses a push-pull port, which can withstand a large current when outputting 1 or 0.
3. Of course, after the MCU is reset, the port state is a certain high level (such as 51 MCU) or high impedance (AVR, etc.). It is not wrong to initialize it in the program! Some compilers can automatically generate code (such as the CVAVR compiler of AVR MCU), and they all initialize the port to high impedance at the beginning of the program. If you want to save code space, you can remove these codes.
4. In addition to Keil UV2, IAR for 8051 compiler is also good, but I think IAR's compiler is mainly aimed at enhanced microcontrollers such as C8051F series and CC2430. For ordinary microcontrollers... it seems to be a waste of talent!
Previous article：Introduction to the Principle of MCU Simulator
Next article：MCU digital filter program
- Popular Resources
- Popular amplifiers
TLC25L2ACDR
Recommended Content
Latest Microcontroller Articles
- Learn ARM development(16)There are many things to learn about ARM, and interrupts are definitely something that needs to be learned. Since the CPU introduced interrupts, it has truly entered the multi-tasking system and greatly improved work efficiency. ...
- Learn ARM development(17)Because all embedded systems use interrupts, how does my S3C44B0 interrupt the process? Then I need to understand the whole process. To understand it in depth, the best way is to write a program ...
- Learn ARM development(18)Last time, we have learned about the interrupt handling process of ARM and how to set the interrupt function. So, does it work like this? The answer is no. Because S3C44B0 has several registers that control ...
- Embedded system debugging simulation toolAfter the embedded hardware system is designed, it needs to be debugged. Whether it is hardware debugging, software debugging or program solidification, debugging simulation tools are needed. ...
- A small question that has been bothering me recently has finally been solved~~Recently, I have not been able to understand the concept of drivers very well. Sometimes I can get a feel for it by combining some USB examples written by others, but because the ARM system does not directly explain the pins like the microcontroller ...
- Learn ARM development (1)
- Learn ARM development (2)
- Learn ARM development (4)
- Learn ARM development (6)
He Limin Column
Microcontroller and Embedded Systems Bible
Professor at Beihang University, dedicated to promoting microcontrollers and embedded systems for over 20 years.
MoreSelected Circuit Diagrams
MorePopular Articles
- LED chemical incompatibility test to see which chemicals LEDs can be used with
- Application of ARM9 hardware coprocessor on WinCE embedded motherboard
- What are the key points for selecting rotor flowmeter?
- LM317 high power charger circuit
- A brief analysis of Embest's application and development of embedded medical devices
- Single-phase RC protection circuit
- stm32 PVD programmable voltage monitor
- Introduction and measurement of edge trigger and level trigger of 51 single chip microcomputer
- Improved design of Linux system software shell protection technology
- What to do if the ABB robot protection device stops
MoreDaily News
- From probes to power supplies, Tektronix is leading the way in comprehensive innovation in power electronics testing
- From probes to power supplies, Tektronix is leading the way in comprehensive innovation in power electronics testing
- Sn-doped CuO nanostructure-based ethanol gas sensor for real-time drunk driving detection in vehicles
- Design considerations for automotive battery wiring harness
- Do you know all the various motors commonly used in automotive electronics?
- What are the functions of the Internet of Vehicles? What are the uses and benefits of the Internet of Vehicles?
- Power Inverter - A critical safety system for electric vehicles
- Analysis of the information security mechanism of AUTOSAR, the automotive embedded software framework
- Brief Analysis of Automotive Ethernet Test Content and Test Methods
- How haptic technology can enhance driving safety
Guess you like
- How to use Bluetooth 4.2 to implement the Internet of Things
- EEWORLD University Hall----Live Replay: Keysight Thanksgiving Month Oscilloscope Lecture Hall
- NDRC responds to chip project failure: whoever supports it will be held responsible for major losses and will be held accountable
- 【GD32450I-EVAL】Transplant touch to LittleVGL
- EEWORLD University - Principles of Electronic Measurement
- About the version of MicroPython?
- 2019 National Undergraduate Electronic Design Competition Summary and Award Ceremony Notice
- Disease data information is uploaded to the cloud in a timely manner NRF9160
- Measuring magnet position using the LSM303AGR magnetometer
- [Evaluation of SGP40] +UART communication test sensor
京公网安备 11010802033920号