ST10F276 datasheet(59/229 Pages) STMICROELECTRONICS

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ST10F276

Bootstrap loader

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5.4.3

ST10 configuration in CAN BSL

When the ST10F276 enters BSL mode via CAN, the configuration shown in Table 31 is

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

Other than after a normal reset, the watchdog timer is disabled, so the bootstrap loading

sequence is not time limited. Pin CAN1_TxD1 is configured as output, so the ST10F276 can

return the identification frame. Even if the internal IFLASH is enabled, a code cannot be

executed from it.

5.4.4

Loading the start-up code via CAN

After sending the acknowledge byte, the BSL enters a loop to receive 128 bytes via CAN1.

Hint: The number of bytes loaded when booting via the CAN interface has been extended to

128 bytes to allow the reconfiguration of the CAN Bit Timing Register with the best timings

(synchronization window, ...). This can be achieved by the following sequence of

instructions:

ReconfigureBaud rate:

MOV

R1,#041h

MOV

DPP3:0EF00h,R1 ; Put CAN in Init, enable Configuration Change

MOV

R1,#01600h

MOV

DPP3:0EF06h,R1 ; 1MBaud at Fcpu = 20 MHz

These 128 bytes are stored sequentially into locations 00’FA40H through 00’FABFH of the

IRAM, allowing up to 64 instructions to be placed into the RAM area. To execute the loaded

code the BSL then jumps to location 00’FA40H, that is, the first loaded instruction. The

bootstrap loading sequence is now terminated; however, the ST10F276 remains in BSL

Table 31.

ST10 configuration in CAN BSL

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.

CAN1 Status/Control register 0000H

Initialized only if Bootstrap via CAN

CAN1 Bit timing register

acc. to ‘0’ frame

Initialized only if Bootstrap via CAN

XPERCON

042DH

XRAM1-2, XFlash, CAN1 and XMISC enabled

P4.6 / CAN1_TxD

‘1’

Initialized only if Bootstrap via CAN

DP4.6

‘1’

Initialized only if Bootstrap via CAN

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