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GD32L23x User Manual
450
Figure 20-2. LPUART character frame
Idle frame
Break frame
Stop
CLOCK
Data frame
Start
bit4
bit5
bit6
bit7
bit0
bit1
bit2
bit3
Start
Start
Stop
Start
or parity bit
8 bit word length (WL = 00), 1 stop bit
Stop
Idle frame
Break frame
CLOCK
Data frame
Start
bit4
bit5
bit6
bit7
bit0
bit1
bit2
bit3
Start
Start
Stop
Start
or parity bit
9 bit word length (WL = 01), 1 stop bit
Stop
bit8
Stop
Idle frame
Break frame
CLOCK
Data frame
Start
bit4
bit5
bit6
bit0
bit1
bit2
bit3
or parity bit
7 bit word length (WL = 10), 1 stop bit
Stop
Start
Start
Stop
Start
Stop
In transmission and reception, the number of stop bits can be configured by the STB[1:0]
bits in the LPUART_CTL1 register:
–
STB[1:0] = 00: 1 stop bit length
–
STB[1:0] = 10: 2 stop bit length
In an idle frame, all the frame bits are logic 1. The frame length is equal to the normal LPUART
frame.
The break frame structure is a number of low bits followed by 2 stop bits.
20.3.2.
Baud rate generation
The baudrate divider is a 20-bits number. The number is used by the baudrate generator to
determine the bit period. The baudrate divider (LPUARTDIV) has the following relationship
with the LPUCLK:
LPUARTDIV=
256×LPUCLK
Baud Rate
(20-1)
Where:
–
LPUARTDIV: The baudrate divider, which is defined in LPUART_BAUD register.
Note
:
1.
The value of LPUART_BAUD[19:0] must be greater than 0x300.