5 Boot management

AN2168

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5

Boot management

Different boot modes are available on ST10F27x devices:

●

The bootstrap mode provides a mechanism to load a program in RAM of the ST10F27x

devices without using internal or external memory.

●

The single chip pin EA allows the device to boot either from the internal flash or from an

external memory.

5.1

Bootstrap loader

The ST10F276 provides the following boot capabilities:

●

Standard bootstrap: This mode downloads a start up program of 32 bytes through the

serial interface or of 128 bytes through the CAN interface after reset in the ST10F276

RAM.

●

Alternate bootstrap: This mode executes a user bootstrap code written by the customer

starting at address 09’0000 if some conditions are met.

●

Selective bootstrap: This mode is a sub-case of the alternate bootstrap mode. It’s triggered

when the conditions required for the alternate bootstrap are not met.

For more details concerning the alternate bootstrap mode, please refer to the ST10F276 user

manual.

The bootstrap mode is selected according to P0L.4 and P0L.5 levels during reset.

Table 3.

ST10F27x bootstrap modes

Example: The following figure illustrates the hardware required for the standard bootstrap

loader via CAN interface. For more details, refer to the ST10F27x user manual.

P0L.4

P0L.5

Bootstrap mode

Comments

0

1

Standard bootstrap

Use a pull up resistor on P4.5 in order to have a

stable level on this pin during bootstrap via CAN. To

avoid high consumption, high resistor values must

be chosen.

For more details please refer to the ST10F27x user

manual

00

Reserved

1

0

Alternate/Selective Bootstrap

The selection between the alternate and selective

bootstrap modes is done by comparing two

signatures to predefined user and alternate

signatures.

1

1

User code

The ST10F27x starts fetching code form internal

ROM or external ROM according to EA pin’s level.