SCM is now overwhelming, a wide variety, so that developers are overwhelmed

The single chip computer is now overwhelming , A wide variety , It's overwhelming for developers , Development is also quite rapid , From the last century 80 years , By then 4 position 8 Bit development to the present all kinds of high-speed MCU ……

Every manufacturer is also in speed 、 Memory 、 One after another in function , uneven ~~ At the same time, a large number of manufacturers with representative single-chip computers have emerged ：Atmel、TI、ST、MicroChip、ARM… Hongjing in China STC The single chip computer is also worth mentioning …

Let's bring you 51、MSP430、TMS、STM32、PIC、AVR、STC The advantages and disadvantages comparison and function embodiment between single chip microcomputer ……

The biggest weakness of single chip microcomputer is the limited computing power , If the encryption requirements are not high , A simple encryption logic can be designed by using a random generator , It is sent after the software completes the calculation in the single chip microcomputer , For example, random numbers can be used to XOR with the content sent , But you need to package and send random numbers , The receiver then reverses the operation in the way of the single chip microcomputer . Design the message format by yourself , Add some simple redundancy verification .

The article is relatively long , More words , You can first open the avatar and pay attention to me , Then take your time ,/// Insert a ： At the beginning of this year, I recorded a set of systematic introductory single chip microcomputer tutorial , If you want, just ask me for it. It's free , I can send a private message ~ Click the black font in the lower left corner of my avatar and I can also get it . I've been relatively idle recently , Take me to finish the design , Take students to provincial or above competitions ///

Of course , There must be many defects in the above method , The great God gate doesn't need to clap bricks , Since the subject said “ Simple encryption ”, Let's use it as a reference .

If you want to be more standardized , You can refer to SM4（SM1、2、3 I don't recommend it ）, However, as mentioned earlier, the computing power of single chip microcomputer is limited , It is not suitable to implement too complex operations .

STC SCM and STM32 Single chip computers are Haval computer structures that use independent data and address buses to access data and program memory .STC SCM is based on MCS-51 Kernel 8 Bit MCU ,STM32 Is based on Cortex-M3 Kernel 32 Bit MCU .

Both have the core operation processor of the computer integrated in a single chip and peripherals with different functions .STC SCM and STM32 SCM is widely used in China , There's a lot of information , Information for getting started 、 resources 、 Tools and software are relatively rich . These characteristics and reality of these two chips , Determines a very important reality at present ： It is necessary for hardware R & D engineers to master and adopt STC SCM and STM32 SCM product development skills .

Ordinary single chip microcomputer and STM32 The difference of stack in SCM

When ordinary single chip microcomputer starts , Don't need to use bootloader Remove the code from the ROM Move to RAM. however STM32 SCM needs .

Here we can first look at the single-chip program execution process , There are three steps for single-chip microcomputer ：

Take command

Analysis instructions

Execution instruction

according to PC To read instructions from program memory , Send to instruction register . Then analyze the execution execution . In this way, the single-chip microcomputer will remove code instructions from the internal program memory , from RAM Access to relevant data .

RAM The speed of fetching is much higher than ROM Of , But ordinary single-chip computers run at a low frequency , So from ROM Slow fetching does not affect .

and STM32 Of CPU High frequency of operation , Far greater than from ROM The speed of reading and writing . So we need to use bootloader Remove the code from the ROM Move to RAM.

Using a stack is like eating in a restaurant , Just order （ Issue an application ）、 pay 、 And eating （ Use ）, When you are full, go , Don't pay attention to cutting vegetables 、 Prepare for dishes and dishes 、 Brush the pot and finish the work , His advantage is fast , But the freedom is small . Using heaps is like making your own favorite dishes , More trouble , But more in line with their own taste , And there's a lot of freedom .

In fact, the stack is some memory units in the single chip microcomputer , These storage units are designated to hold some special information , Like the address （ Protect breakpoints ） And data （ Protection site ）.

If you have to add a few characteristics to him, it's ：

The contents of these storage units are interrupted during program execution , Some relevant parameters of the accident site . If you don't save these parameters , The single chip computer can't go back to the main program to continue after executing the interrupt function .

The addresses of these storage units are recorded in a stack pointer （SP） The place of .

combination STM32 Development of stack

It can be seen from the above description , How to occupy heap and stack in code . Maybe many people still can't understand , Combine here STM32 Stack related content in the development process of .

Friends interested in MCU can come to me , I recorded some introductory tutorials about MCU , If you need children's shoes, just ask me for them , Free of charge , Private confidence in me “ Miss Lin ” You can take ～ Click to open my avatar to receive