AN3155 datasheet(16/37 Pages) STMICROELECTRONICS

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Bootloader command set

AN3155

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DocID17066 Rev 6

3.5

Go command

The Go command is used to execute the downloaded code or any other code by branching

to an address specified by the application. When the bootloader receives the Go command,

it transmits the ACK byte to the application. After the transmission of the ACK byte, the

bootloader waits for an address (4 bytes, byte 1 is the address MSB and byte 4 is LSB) and

a checksum byte, then it checks the received address. If the address is valid and the

checksum is correct, the bootloader transmits an ACK byte, otherwise it transmits a NACK

byte and aborts the command.

When the address is valid and the checksum is correct, the bootloader firmware performs

the following:

•

it initializes the registers of the peripherals used by the bootloader to their default reset

values

•

it initializes the user application’s main stack pointer

•

it jumps to the memory location programmed in the received ‘address + 4’ (which

corresponds to the address of the application’s reset handler).

For example if the received address is 0x0800 0000, the bootloader will jump to the

memory location programmed at address 0x0800 0004.

In general, the host should send the base address where the application to jump to is

programmed

Figure 10. Go command: host side

Note:

Valid addresses for the Go command are in RAM or Flash memory (refer to STM32 product

datasheets and to the “STM32 microcontroller system memory boot mode” application note

- AN2606 for more details about the valid memory addresses for the device you are using).

AN3155 Datasheet(PDF) 16 Page - STMicroelectronics