ST10F276E datasheet(66/235 Pages) STMICROELECTRONICS

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Bootstrap loader

ST10F276E

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Doc ID 12303 Rev 3

5.5

Comparing the old and the new bootstrap loader

Table 33 and Table 34 summarize the differences between the old ST10 (boot via UART

only) bootstrap and the new one (boot via UART or CAN).

5.5.1

Software aspects

As the CAN1 is needed, XPERCON register is configured by the bootstrap loader code and

bit XPEN of SYSCON is set. However, as long as the EINIT instruction is not executed (and

it is not in the bootstrap loader code), the settings can be modified. To do this, perform the

following steps:

Disable the XPeripherals by clearing XPEN in SYSCON register. Attention: If this part

of the code is located in XRAM, it will be disabled.

Enable the needed XPeripherals by writing the correct value in XPERCON register.

Set XPEN bit in SYSCON.

5.5.2

Hardware aspects

Although the new bootstrap loader is designed to be compatible with the old bootstrap

loader, there are a few hardware requirements for the new bootstrap loader as summarized

in Table 34.

Table 33.

Software topics summary

Former bootstrap loader

New bootstrap loader

Comments

Uses only 32 bytes in Dual-Port

RAM from 00’FA40h

Uses up to 128 bytes in Dual-

Port RAM from 00’FA40h

For compatibility between boot

via UART and boot via CAN1,

please avoid loading the

application software in the

00’FA60h/00’FABFh range.

Loads 32 bytes from UART

(boot via UART mode)

Same files can be used for boot

via UART.

User selected Xperipherals can

be enabled during boot (Step 3

or Step 4).

Xperipherals selection is fixed.

User can change the

Xperipherals selections through

a specific code.

Table 34.

Hardware topics summary

Former bootstrap loader

New bootstrap loader

Comments

P4.5 can be used as output in

BSL mode.

P4.5 cannot be used as user

output in BSL mode, but only as

CAN1_RxD or input or address

segments.

Level on CAN1_RxD can

change during boot Step 2.

Level on CAN1_RxD must be

stable at ‘1’ during boot Step 2.

External pull-up on P4.5

needed.

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