Serial Boot Configuration - STMicroelectronics SPC572L series Reference Manual

Boot Assist Flash (BAF)
52.2.6

Serial boot configuration

52.2.6.1 LINFlexD configuration
Boot using UART protocol is implemented by LINFlexD module.
Note: See the pin configuration table in the configuration for pins used by the LINFlexD module.
When Serial Boot mode is started the LINFlexD_Rx is configured as an input and
multiplexed to the LINFlexD_0 module. The LINFlexD_Tx remains in a passive input state
until the first byte of protocol is received. It is then configured as an output and multiplexed
to LINFlexD module. The application may not be using the Serial Boot Mode function, and
may be using the pin used by LINFlexD_Tx as an input, which may have some external
hardware driving the pin. Inadvertently driving this pin as an output would cause contention
and possible damage.
The LINFlexD module operates in half-duplex mode. The interface is either transmitting a
byte or receiving a byte, but never both at the same time. It is expected that LINFlexD pins
are connected to a physical layer bus driver/receiver (PHY). Many PHYs enforce half-duplex
mode by using a single data channel for both transmitting and receiving data (such as LIN or
CAN). The side effect of this is that all data transmitted on Tx pin is also received on Rx pin.
To prevent the LINFlexD module receiving its own transmission, the Rx pin is blocked during
Tx pin transmission.
The LINFlexD controller is configured to operate at a baud rate of 250 kbaud with the
IRCOSC as reference clock, using ane 8-bit data frame without parity bit and 1 stop bit.
52.2.6.2 M_CAN configuration
The M_CAN controller is configured to operate at a baud rate equal to crystal frequency
divided by 40, using the standard 11-bit identifier format detailed in CAN 2.0A specification
(see Table 880
The Bit timing is configured as shown in
1556/2058
Figure 926. LINFlexD bit timing in UART mode
Start
D0 D1
bit
for baud rates).
DocID027809 Rev 4
Byte Field
D2 D3 D4
Figure 927 (M_CAN Bit Timing)
D5 D6 D7
RM0400
Stop
bit