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M0A21/M0A23 Series
May 06, 2022
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Rev 1.02
M0
A21
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SE
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TEC
H
NICAL
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ANUAL
6.11.5.6 UART Controller Wake-up Function
The UART controller supports wake-up system function. The wake-up function includes nCTS pin,
incoming data wake-up, Received Data FIFO reached threshold wake-up, RS-485 Address Match (AAD
mode) wake-up and Received Data FIFO threshold time-out wake-up function. CTSWKF
(UART_WKSTS[0]), DATWKF (UART_WKSTS[1]), RFRTWKF (UART_WKSTS[2]), RS485WKF
(UART_WKSTS[3]) or TOUTWKF (UART_WKSTS[4]) cause the wake-up interrupt flag WKIF
(UART_INTSTS[6]) is generated. If the WKIEN (UART_INTEN[6]) enabled, the wake-up interrupt flag
WKIF (UART_INTSTS[6]) cause the wake-up interrupt WKINT (UART_INTSTS[14]) generated.
nCTS pin wake-up :
When the system is in Power-down mode and WKCTSEN (UART_WKCTL[0]) is set, the toggle of nCTS
pin can wake-up system. If the WKCTSEN (UART_WKCTL[0]) is enabled, the toggle of nCTS pin cause
the nCTS wake-up flag CTSWKF (UART_WKSTS[0]) generated. The nCTS wake-up is shown in Figure
6.11-5 and Figure 6.11-6.
nCTS Wake-up Case 1 (nCTS transition from low to high)
Power-down mode
HCLK
nCTS
CTSWKF
stable count
CPU run
CTSACTLV (UART_MODEMSTS[8]) = 0
Note:
Stable count means HCLK source recovery stable count.
Figure 6.11-5 UART nCTS Wake-up Case1
nCTS Wake-up Case 2 (nCTS transition from high to low)
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 6.11-6 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. The incoming data wake-up is
shown in Figure 6.11-7.
Note1:
The UART controller clock source should be selected as HIRC and the compensation time for