In embedded system, must the program code in flash be moved to ram to run?

This problem , The core still depends on what chip scheme you use ！

Embedded system involves a huge technology stack , It's not just what you understand ARM+Linux nothing more .

I work in 11 year , I only dare to say that I am familiar with one of the directions .

Embedded system , The core unit is the core of the whole system ” The brain ”, Similar to a computer cpu.

I loosely call it a processor , So as not to spray .

Different processors , The performance is different , In terms of performance, it can be divided into the following ：

 

By different embedded processors , It also leads to different career directions , There are several mainstream ：

1. MCU Engineer

2.Linux Drive development

3.Linux System Development Engineer

4.Linux Application Engineer

5. Android system development engineer

6.FPGA/DSP Development

 

Different processor types run programs differently , Can't generalize .

I compare the two mainstream ：

1. Embedded microcontrollers (MCU)

That is, MCU , such as 8051、LPC2132、STM32 wait 、 Chip program storage areas are all on-chip nor flash.

Nor flash Can be directly like memory RAM Same addressing , So MCU can directly from the inside FLASH Run the program .

2. Embedded microprocessors MPU

Generally, it is what people say ARM+Linux.

But not all of them ARM All need to run Linux Of ,STM32 Also belong to ARM, But most of them are ” Bare metal programming ”, Run at most RTOS.

commonly ARM+Linux The program exists in the external memory , such as nand flash wait .

Before the program is executed , From external storage ( such as nand flash) Put the reading program in ram Run in ,cpu from ram It reads programs and data .

3. summary

Whether it needs to be transported to ram, It depends on what chip scheme you use .

You can simply understand it as , If you are developed by MCU , Is directly from the film nor flash Read program execution .

If it is ARM+Linux It needs to be transported to ram perform .

Single chip microcomputer is generally hundreds of kb The program project is already quite large , and ARM+Linux Just a few dozen MB, The program of this volume , Built in Nor flash Words , Whether it can be realized technically will not be mentioned for the time being , The cost is immeasurable .

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