另外不懂你在纠结什么,参考手册上写的很清楚么:
USART_CR1的
M:Word Length
This bit determines the word length. It is set or cleared by software.
0:1 start bit, 8 data bits, n stop bit
1:1 start bit, 9 data bits, n stop bit
PCE: Parity control enable
This bit selects the hardware parity control.when the parity control is enabled, the computed parity is inserted at the MSB position(9th bit if M=1;8th bit if M=0) and parity is checked on the received data.
0: parity control disabled
1: parity control enabled.