ST SPC560P34 - Figure 489. BAM Rate Measurement Flow During UART Boot

RM0046 Boot Assist Module (BAM)
Doc ID 16912 Rev 5 823/936
The LINFlex module is configured to work in UART mode with the calculated baud rate.
Then an acknowledge byte (0x59, ASCII char “Y”) is sent.
From this point, the BAM follows the normal UART mode boot protocol (see Figure 489).
Figure 489. BAM rate measurement flow during UART boot
Choosing the host baud rate
The calculation of the UART baud rate from the length of the first 0 byte that is received,
allows the operation of the boot loader with a wide range of baud rates. However, to ensure
proper data transfer, the upper and lower limits have to be kept.
Start
UART_RX == 0
NO
NO
YES
YES
UART_RX
configured as
GPIO input
Stop STM
Read elapsed time
Calculate baud rate
Baud rate
configuration
UART_RX == 1
Follow normal
UART boot protocol
Start STM
UART_RX pin is configured
to work with LINFlex module.
LINFlex module is configured in UART
mode with calculated baud rate.