Nations Technologies Inc.
Tel
:
+86-755-86309900
:
Address: Nations Tower, #109 Baoshen Road, Hi-tech Park North.
Nanshan District, Shenzhen, 518057, P.R.China
469
/
631
Figure 22-11 CTS flow controls
Multiprocessor communication
USART allows multiprocessor communication. The principle is: multiple processors communicate through USART,
and it is necessary to determine who is the master device, and the remaining processors are all slave devices. The TX
output of the master device is directly connected to the RX port of all slave device. The TX outputs of the slaves are
logically AND together and connected to the RX inputs of the master.
When multi-processor communication is performed, the slave devices are all in mute mode, and the host uses a
specific method to wake up a slave device to be communicated when needed, so that the slave device is in an active
state and transmits data with the master device.
The USART can wake up from mute mode by idle line detection or address mark detection.
Idle line detection
The idle line detection configuration process is as follows:
1.
Configure the USART_CTRL1.WUM bit to 0, and the USART performs idle line detection;
2.
When USART_CTRL1.RCVWU is set (which can be automatically controlled by hardware or written by
software under certain conditions), USART enters mute mode. In mute mode, none of the receive status bits are
set, and all receive interrupts are disabled;
3.
As shown in the Figure 22-12 below, when an idle frame is detected, USART is woken up, and then
USART_CTRL1.RCVWU is cleared by hardware. At this time, USART_STS.IDLEF is not set.
CTSF = 1
CTSF = 1
CTS line
Data register
Data 2
empty
Data 3
Data 2
Data 3
Data 1
empty
Start
Bit
Stop
Bit
Stop
Bit
Start
Bit
Idle
CTS = 1,
Transmit delay
TX line
Writing Data 3 in
Data register
CTS = 0,
Transmit Data 3