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NUC126
Aug. 08, 2018
Page
865
of 943
Rev 1.03
NUC12
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NUA
L
Power-down mode
HCLK
nCTS
stable count
CPU run
CTSACTLV (UART_MODEM[8]) = 1
CTSWKF
Note:
Stable count means HCLK source recovery stable count.
Figure 6.23-6 UART nCTS Wake-up Case2
Incoming Data Wake-up
When system is in Power-down mode and the WKDATEN (UART_WKCTL [1]) is set, the toggle of
incoming data (UART_RXD) pin can wake-up the system. In order to receive the incoming data after
the system wake-up, the STCOMP (UART_DWKCOMP[15:0]) shall be set. These bits field of
STCOMP indicate how many clock cycle selected by UART_CLK do the UART controller can get the
1
st
bit (start bit) when the system is wakeup from power-down mode.
When incoming data wakes system up, the incoming data will be received and stored in FIFO. If the
WKDATEN (UART_WKCTL[1]) is enabled, the toggle of incoming data (UART_RXD) pin cause the
incoming data wake-up flag DATWKF (UART_WKSTS[1]) is generated.
Note1:
The UART controller clock source should be selected as HIRC and the compensation time for
start bit is about 35us. It means that the value of STCOMP (UART_DWKCOMP[15:0]) can be set as
774.
Note2:
The
value
of
BRD(UART_BAUD[15:0])
should
be
greater
than
STCOMP
(UART_DWKCOMP[15:0]).
Power-down mode
UART_CLK
UART_RXD
DATWKF
UART_CLK stable count
CPU run
start
HCLK
stable count
Note1:
Stable count means HCLK source recovery stable count.
Note2:
UART_CLK stable count means UART clock source recovery stable count.
Figure 6.23-7 UART Data Wake-up
Received Data FIFO Reached Threshold Wake-up
The received data FIFO threshold reached wake-up function is enabled by setting WKRFRTEN
(UART_WKCTL[2]). In Power-down mode, when the number of received data in RX FIFO reaches the
threshold value RFITL (UART_FIFO[7:4]), it can wake-up the system. If the WKRFRTEN
(UART_WKCTL[2]) is enabled, the number of received data in RX FIFO reaches the threshold value
RFITL (UART_FIFO[7:4]) cause the received data FIFO reached threshold wake-up flag RFRTWKF
(UART_WKSTS[2]) is generated.
Note:
The UART controller clock source should be selected as LXT in Power-down mode to receive
data.