Detailed explanation of STM32 ISP settings and usage instructions

1. Overview of STM32 BOOT

The storage media corresponding to the three startup modes of STM32 are all built-in to the chip, they are:

User Flash: BOOT1=x BOOT0=0 The built-in Flash of the chip, i.e. the main memory Flash

SRAM: BOOT1=1 BOOT0=1 The SRAM area built into the chip is the memory. 

System memory: BOOT1=0 BOOT0=1 A specific area inside the chip is called system memory. A Bootloader is preset in this area when the chip leaves the factory, which is usually called the ISP program. The content of this area cannot be modified or erased after the chip leaves the factory, that is, it is a ROM area.

      There are two pins BOOT0 and BOOT1 on each STM32 chip. The level status of these two pins when the chip is reset determines which area the program starts from after the chip is reset, see the table below:

BOOT1=x BOOT0=0 Boot from user flash memory, which is the normal working mode.

BOOT1=0 BOOT0=1 Boot from system memory. The program function started in this mode is set by the manufacturer.

BOOT1=1 BOOT0=1 Boot from built-in SRAM. This mode can be used for debugging.

It should be noted that the built-in SRAM is generally not used for startup (BOOT1=1 BOOT0=1), because the data in the SRAM will be lost after the power is off. In most cases, SRAM is only used for debugging, and it can also be used for other purposes. For example, to do local diagnosis of faults, write a small program to load it into the SRAM to diagnose other circuits on the board, or use this method to read and write the Flash or EEPROM on the board. This method can also be used to remove the read and write protection of the internal Flash. Of course, when removing the read and write protection, the content of the Flash is also automatically cleared to prevent malicious software from copying.

Generally, both BOOT0 and BOOT1 jumpers are set to 0 (GND), which means the system runs normally from the on-chip Flash. However, in the case of ISP download, you need to set BOOT0=1 and BOOT1=0. After the download is complete, connect the BOOT0 jumper back to 0 so that the system can run normally.

For general applications, you can directly ground the BOOT0 and BOOT1 pins without setting jumpers. When using the IAR debugger, you can choose RAM debugging or Flash debugging, which has nothing to do with the configuration of BOOT0 and BOOT1.

When I was designing the program for stm32, I encountered a conflict between the nss pins of spi3 and the pins of JTAG. So in order to solve this problem and make spi3 work normally, I disabled the JTAG function through the library function GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable,ENABLE);, so that spi3 can be used normally, but the result is that the program cannot be burned through JTAG! Therefore, the topic of burning the program through the ISP serial port has surfaced!

2. The usage process of STM32 ISP tool.