ST10F276 datasheet(66/229 Pages) STMICROELECTRONICS

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Bootstrap loader

ST10F276

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5.6.4

ST10 configuration in alternate boot mode

When the ST10F276 enters BSL mode via CAN, the configuration shown in Table 35 is

automatically set (values that deviate from the normal reset values are marked in bold).

Even if the internal IFLASH is enabled, a code cannot be executed from it.

As the XFlash is needed, XPERCON register is configured by the ABM 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:

●

Copy in DPRAM a function that will

–

disable the XPeripherals by clearing XPEN in SYSCON register,

–

enabled the needed XPeripherals by writing the correct value in XPERCON

–

set XPEN bit in SYSCON,

–

return to calling address.

●

Call the function from XFlash

The changing of the XPERCON value cannot be executed from the XFlash because the

XFlash is disabled by the clearing of XPEN bit in SYSCON.

5.6.5

Watchdog

As for standard boot, the Watchdog timer remains disabled during Alternate Boot Mode. In

case a Watchdog reset occurs, a software reset is generated.

Note:

See note from Section 5.2.7 concerning software reset.

5.6.6

Exiting alternate boot mode

Once the ABM mode is entered, it can be exited only with a software or hardware reset.

Note:

See note from Section 5.2.7 concerning software reset.

Table 35.

ST10 configuration in alternate boot mode

Function or register

Access

Notes

Watchdog timer

Disabled

0404H(1)

In Bootstrap modes (standard or alternate) ROMEN, bit 10 of SYSCON, is always set regardless of EA pin

level. BYTDIS, bit 9 of SYSCON, is set according to data bus width selection via Port0 configuration.

XPEN bit set

Context pointer CP

FA00H

Stack pointer SP

FA40H

FC00H

acc. to startup config.(2)

BUSCON0 is initialized with 0000h, external bus disabled, if pin EA is high during reset. If pin EA is low

during reset, BUSACT0, bit 10, and ALECTL0, bit 9, are set enabling the external bus with lengthened ALE

signal. BTYP field, bit 7 and 6, is set according to Port0 configuration.

XPERCON

002DH

XRAM1-2, XFlash, CAN1 enabled

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