RM0319 datasheet(40/368 Pages) STMICROELECTRONICS

40 / 368 page

BootROM

RM0319

40/368

Doc ID 022640 Rev 3

Figure 8.

Boot flow

5.6.1

Serial NOR Flash boot

In NOR Boot, BootROM tries to authenticate X-Loader in the first sector of Flash. The load

address of X-Loader (ih_load) is specified in the 64-byte X-Loader header.

Authentication is performed in 3 steps:

The value of bits 3:0 in the Boot_Strap_Reg (address 0xB3000000) is compared with

0x3

ih_magic is compared with 0x27051956

ih_hcrc is compared with the calculated CRC of the header

If the authentication is successful, then BootROM copies X-Loader from Flash to ‘shadow

memory’ area (address pointed to by ih_load) and jumps to it.

If X-Loader authentication fails, or any other error occurs during serial NOR boot, BootROM

shifts to USB boot.

5.6.2

Serial (UART0) boot

Serial boot initializes the UART0 IP and uses the X-modem protocol to receive the X-Loader

image at a fixed baud rate of 11250 bits per second (bps). It then runs the X-Loader image

which initializes the PLLs and DDR and then returns back the control to the boot code. After

this, X-modem protocol is again used to download the U-Boot image into DDR and then the

image is run from there. To be noted that this booting mode does not require any non-

volatile memory to be present on the board.

Start

Initialize

interrupts

SMI initialization

Test boot type

Proceed to

specific boot

Boot

successful?

Infinite loop

Yes

Jump to X-loader/ U_Boot

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