Boot configuration

AN2419

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Boot configuration

In the STR750, 4 different boot modes can be selected by means of the BOOT[1:0] pins as

shown in Table 2.

Figure 11.

Boot mode selection implementation example

This aliases the physical memory associated with each boot mode to Block 000 (boot

memory).The value of the BOOT pin is latched on the 4th rising edge of CK_SYS after

Reset.

It is up to the user to manage the BOOT1 and BOOT0 pins at reset release to select the

required boot mode. Note that the user should also manage these pins when exiting

Standby mode as the BOOT pins are resampled.

Even when aliased in the boot memory space, the related memory (FLASH, SRAM or SMI)

is still accessible at its original memory space.

After this start-up delay has elapsed, the ARM CPU will start code execution from the boot

memory space, located at the bottom of the memory space starting from 0x0000_0000h.

The application can read the status of the boot pins that was latched at start-up and change

the memory aliasing on-the-fly by modifying the SW_BOOT bits in the CFG_GLCONF

register.

Caution:

The TEST pin of the STR75x must always be forced to ground (ST reserved test pin)

Table 2.

Boot modes

BOOT Mode

Selection Pins

Boot Mode

Aliasing

Note

BOOT1

BOOT0

0

0

Embedded Flash

Embedded FLASH sector

B0F0 mapped at 0h

All FLASH sectors

accessible except

SystemMemory

sector

1

0

Embedded SRAM

Embedded SRAM mapped

at 0h

0

1

SystemMemory

SystemMemory mapped

at 0h

-

11

External SMI Serial Flash

memory

SMI Bank 0 mapped at 0h

-

STR75x

BOOT0

* these values are given only as typical example

10K*

3V3

10K*

3V3

BOOT1

TEST

GND