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GD32F10x User Manual
437
16.3.7.
Multi-processor communication
In multiprocessor communication, several USARTs are connected as a network. It will be a
big burden for a device to monitor all of the messages on the RX pin. To reduce the burden
of a device, software can put an USART module into a mute mode by setting the RWU bit in
USART_CTL0 register.
If a USART is in mute mode, all of the receive status bits cannot be set. Software can wake
up the USART by resetting the RWU bit.
The USART can also be wake up by hardware by one of the two methods: idle frame method
and address match method.
The idle frame wake up method is selected by default. When an idle frame is detected on the
RX pin, the hardware clears the RWU bit and exits the mute mode. When wake up at an idle
frame, the IDLEF bit in USART_STAT is not set.
When the WM bit of in USART_CTL0 register is set, the MSB bit of a frame is detected as the
address flag. If the address flag is high, the frame is treated as an address frame. If the
address flag is low, the frame is treated as a data frame. If the LSB 4 bits of an address frame
are the same as the ADDR[3:0] bits in the USART_CTL1 register, the hardware clears the
RWU bit and exits the mute mode. The RBNE bit is set for the frame that wakes up the USART.
The status bits are available in the USART_STAT register. If the LSB 4 bits of an address
frame differ from the ADDR[3:0] bits in the USART_CTL1 register, the hardware sets the RWU
bit and enters mute mode automatically. In this situation, the RBNE bit is not set.
If the address match method is selected, the receiver does not check the parity value of an
address frame by default. If the PCEN bit in USART_CTL0 is set, the MSB bit will be checked
as the parity bit, and the bit preceding the MSB bit is detected as the address flag.
16.3.8.
LIN mode
The local interconnection network mode is enabled by setting the LMEN bit in USART_CTL1.
The CKEN, STB[1:0] bits in USART_CTL1 and the SCEN, HDEN, IREN bits in USART_CTL2
should be reset in LIN mode.
When transmitting a normal data frame, the transmission procedure is the same as the normal
USART mode. The data bits length must be 8. When the SBKCMD bit in USART_CTL0 is set,
the USART transmits continuous 13 ‘0’ bits, following by 1 stop bit.
The break detection function is totally independent from the normal USART receiver. So a
break frame can be detected during the idle state or during a frame. The expected length of
a break frame can be selected by LBLEN in USART_CTL1. When the RX pin is detected at
low state for a time that is equal to or longer than the expected break frame length (10 bits
when LBLEN=0, or 11 bits when LBLEN=1), the LBDF in USART_STAT is set. An interrupt
occurs if the LBDIE bit in USART_CTL1 is set.
Содержание GD32F10 Series
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Страница 416: ...GD32F10x User Manual 416 shadow register updates every update event ...
Страница 427: ...GD32F10x User Manual 427 value ...
Страница 518: ...GD32F10x User Manual 518 These bits are not used in SPI mode ...