
GD32L23x User Manual
457
20.3.7.
Multi-processor communication
In multiprocessor communication, several LPUARTs 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, the MEN bit in LPUART_CTL0 register is used to enable the mute mode function,
software can put an LPUART module into a mute mode by writing 1 to the MMCMD bit in
LPUART_CMD register.
If a LPUART is in mute mode, all of the receive status bits cannot be set. The LPUART 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. If the RWU bit is reset, an idle frame
is detected on the RX pin, he IDLEF bit in LPUART_STAT will be set. If the RWU bit is set, an
idle frame is detected on the RX pin, the hardware clears the RWU bit and exits the mute
mode. When it is woken up by an idle frame, the IDLEF bit in LPUART_STAT will not be set.
When the WM bit of in LPUART_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 or 7 bits, which are
configured by the ADDM bit of the LPUART_CTL1 register, of an address frame is the same
as the ADDR bits in the LPUART_CTL1 register, the hardware will clear the RWU bit and
exits the mute mode. The RBNE bit will be set when the frame that wakes up the LPUART.
The status bits are available in the LPUART_STAT register. If the LSB 4/7 bits of an address
frame defers from the ADDR bits in the LPUART_CTL1 register, the hardware sets the RWU
bit and enters mute mode automatically. In this situation, the RBNE bit is not set.
If the PCEN bit in LPUART_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 bit. If the ADDM bit is set and the receive
frame is a 7bit data, the LSB 6 bits will be compared with ADDR[5:0]. If the ADDM bit is set
and the receive frame is a 9bit data, the LSB 8 bits will be compared with ADDR[7:0].
Note:
If the MEN bit is set, the WM bit is reset and the RWU bit is reset, an idle frame is
detected on the RX pin, the IDLEF bit will be set. If the RWU bit is set, the IDLEF is not set.
20.3.8.
Half-duplex communication mode
The half-duplex communication mode is enabled by setting the HDEN bit in LPUART_CTL2.
Only one wire is used in half-duplex mode. The TX and RX pins are connected together
internally. The TX pin should be configured as IO pin. The conflicts should be controlled by
the software. When the TEN bit is set, the data in the data register will be sent.
20.3.9.
Wakeup from Deep-sleep mode
The LPUART is able to wake up the MCU from Deep-sleep mode by the standard RBNE
interrupt or the WUM interrupt.