Talking about arm and program download

What 1.ARM is.

Everyone is familiar with the single-chip microcomputer should be 51 single-chip microcomputer, in fact, 51 single-chip microcomputer refers to a series of single-chip microcomputer, there are many kinds. Baidu Encyclopedia above is said: to all compatible with the Intel 8031 instruction system of the single-chip computer collectively. So we will be on the market to buy Intel's 80c51 87c51 Aidmer 89C51 89S52 STC (domestic macro crystal) SCM 89C51 89C52 89c516 and so on are 51 single-chip microcomputer. Therefore, the 51-core (compatible with the Intel 8031 Command System) of the microcontroller is 51 single-chip microcomputer.

ARM is all processors that support the RISC instruction set (compact instruction set), which means that the controller using the arm core belongs to arm. The arm core is where the controller is operating, developed by the arm company. Different companies on the arm core plus I/O controller, ad/da modulus conversion module, UART serial port module, Iic,spi,can and so on the communication module, that is, different companies on the ARM processor two times development. After two development of arm, it became SOC (System on chip) chip system, for example, STM developed two CONTEX-M3 version of ARM processor, and STM32, Freescale Corporation ( March 2015 was acquired by NXP in September 2016 by Qualcomm, and the CONTEX-M4 version of the ARM processor was developed two times by the company's K60.

2.ARM compared to other types of processors why processing speed faster.

ARM is defined as: ARM is all processors that support RISC instruction sets (compact instruction sets). Obviously, the advantages of ARM are related to its characteristics (support RISC instruction set). Do not understand this is generally not understand the RISC instruction set is something. Let's talk about what the instruction set is. The instruction set is stored inside the CPU (for ARM processors are stored in the arm core) of the hard program, the essence of the simplified instruction set is the old instruction set is the complex instruction set is truncated. Our CPU executes the instruction by comparing the instruction with the instructions in the internal instruction set, and then performing the corresponding operation when the corresponding instruction is found. If we need to compare instructions in our instruction set, we will shorten the comparison between the instructions we write to the CPU and the instruction set, so our CPU processing instructions will be faster. However, there are some very infrequently used instructions in another place, if the CPU can not find the corresponding instructions in the truncated instructions to go to the place of the less common instructions to compare the search (90% of the situation will be found, almost no more than the common command out of the comparison)

3. How to download the program to the ARM controller.

Generally use the Jtag downloader download, also can use USB, also can use the network. (USB download and network download all require the ARM controller with Boot program support)

4. How the program downloaded to arm is stored.

Bare-Metal program: Download with JTAG is downloaded to flash inside, support direct download bare-metal program, the program from can be placed to Norflash also can put to Nandflash (download software can be selected on the option of downloading) Advantages: stable, reliable disadvantage: compared to the network and USB download speed is very slow ( Arm Download Bare Metal program only with Jtag download)

USB download or network download: This kind of download needs the board inside a program, that is, the so-called Boot program (boot program must be JTAG download to the board), if the boot program in Norflash in this way to download the program to Nandflash, Instead, download it to Norflash

5. Download the difference between the program to Norflash and Nandflash.

NORFLASH:CPU can execute the program directly, and the Norflash 0 address is the 0 address that the CPU thinks

NANDFLASH:CPU can not be directly executed, the hardware automatically copy the Nandflash program into the SDRAM, and then execute.

Small introduction to 6.NandFlash and Norflash (Flash is divided into Nandflash and Norflash)

Nandflash: Large capacity, cheap, generally on arm with 512M nandflash, program download to nandflash than download to Norflash faster. But not directly inside the Nandflash run the program, because of large capacity, cheap reason, buy nandflash inside there is bad block is normal phenomenon, do not affect the use, use Nandflash also need a Nandflash controller use ( Samsung ARM9 Core S3C2440 Integrated Nandflash Controller)

Norflash: Small capacity, high price, general arm controller with 2M, you can directly run the program