AN3154 datasheet(19/34 Pages) STMICROELECTRONICS

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AN3154

Bootloader command set

After sending an ACK message to the application, 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

Note:

The Jump to the application works only if the user application sets the vector table correctly

to point to the application address.

The valid addresses for the Go command are in RAM or Flash memory (refer to Section 3.1:

Get command for more details about the valid memory addresses for the device you are

using). All other addresses are considered not valid and are NACKed by the device.

When an application is loaded into RAM and then a jump is made to it, the program must be

configured to run with an offset to avoid overlapping with the first RAM memory used by the

bootloader firmware (refer to Section 3.1: Get command for more details about the RAM

offset for the device you are using).

Figure 14. Go command: host side

1. See product datasheet for valid addresses.

The host sends the bytes as follows

Go command message: Std ID = 0x21, DLC = 0x04, data[0] = 0xXX: MSB address,...data[3]

= 0xYY LSB address.

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