DocID13284 Rev 2 319/564
UM0404 The bootstrap loader
Note: In most cases (24 MHz, 32 MHz, 40 MHz of CPU frequency and 125, 250, 500 or 1 Mbit/s of
bitrate) there is no error. Anyway, it is better to check the error with the real application
parameters.
The content of the Bit Timing register will be: 0x1640. This gives a sample point at 80%.
Note: The (Re)Synchronization Jump Width is fixed to 2 time quanta.
15.4.7 Bootstrap via CAN
After the bootstrap phase, ST10F276x CAN module is configured as follow:
• The pin P4.6 is configured as output (the latch value is ‘1’ = recessive) to assume
CAN1_TxD function.
• The MO2 is configured to output the acknowledge of the bootstrap with the standard
identifier E6h, a DLC of 3 and Data0 = D5h, Data1&2 = IDCHIP.
• The MO1 is configured to receive messages with the standard identifier 5h. Its
acceptance mask is set in order that all bits must match. The DLC received is not
checked: the ST10 expects only 1 byte of data at a time.
No other message is sent by the ST10F276 after the acknowledge.
Note: The CAN boot waits for 128 byte of data instead of 32 (see UART boot). This is done in
order to allow the User to reconfigure the CAN Bitrate as soon as possible.
15.5 Comparing the old and the new bootstrap loader
The following tables summarize the differences between the old ST10 (boot via UART only)
bootstrap and the new one (boot via UART or CAN).
15.5.1 Software aspects
As the CAN1 is needed, XPERCON register is configured by the bootstrap loader code and
bit XPEN of SYSCON is set. Anyway, as long as the EINIT instruction is not executed (and it
Table 47. Software topics summary
Previous bootstrap loader
ST10F27x 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, avoid loading the
application software in the
00’FA60h/00’FABFh range.
Load 32 bytes from UART
Load 32 bytes from UART
(boot via UART mode)
Same files can be used for boot via
UART.
User selected X-
Peripherals can be enabled
during boot (step 3 or step
4)
X-Peripherals selection is
fixed.
You can change the X-Peripherals
selections through a specific code.
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