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M0A21/M0A23 Series
May 06, 2022
Page
503
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
ABREN
USCI_DATAIN0
CLKDIV
DSCNT
BRDETITV
ABRDETIF
Timing
measurement
counter
1 2 3
……………
.
0
N-2 N-1 N
1 2 3
……………
.
0
N-2 N-1 N
1 2 3
……………
.
0
N-2 N-1 N
1 2 3
……………
.
0
N-2 N-1 N
Falling edge clear the TMCNT
N/2
N/2
N/2
N/2
1
st
falling edge
2
nd
falling edge
3th falling edge
4th falling edge
Clear this bit by H/W at the 4th falling edge
0
N/2
Can be cleared by write 1
Enable this bit by User
A
A
Figure 6.13-5 UART Auto Baud Rate Control
Auto Flow Control
The UART supports hardware auto-flow control that provides nRTS flow control by indicator RXFULL
(UUART_BUFSTS[1]) on receiver buffer. When the buffer is full (RXFULL = 1), the nRTS is de-asserted.
The UART also provides nCTS flow control on transmitter. The nCTS is used to control the transmitted
data is sent out when the nCTS is asserted.
RS-485 Support
The UART controller can play the role of the RS-485 master transmitter will identify an address character
by setting the parity (9-th bit) to 1. For data characters, the parity is set to 0. Software can use the bit15
of each data to control the parity bit (PARITYEN (UUART_PROTCTL[1]) be set) when the STICKEN
(UUART_PROTCTL[26]) is set. For example, if the STICKEN is set to 1 and data sequence are 0x8015,
0x8033, 0x0055, 0x0033 and 0x80AA the transmitted parity of data 0x15, 0x33, 0x55 0x33 and 0xAA
will be 1, 1, 0, 0 and 1.
The UART controller can also play as an RS-485 addressable slave, the protocol-related error of
PARITYERR (UUART_PROTSTS[5]) can be acted as the address bit detection when the PARITYEN
(UUART_PROTCTL[1]),
EVENPARITY
(UUART_PROTCTL[2])
and
STICKEN
(UUART_PROTCTL[26]) were set. If the PARITYERR was set, it means that the address bit in the
received bus is detected otherwise, the data is received into Buffer.
Wake-up Function
The USCI Controller in UART mode supports wake-up system function. The wake-up source includes
incoming data and nCTS pin. Each wake-up source description is as follows:
(a) Incoming data wake-up
When system is in power-down and both of the WKEN (UUART_WKCTL[0]) and DATWKEN
(UUART_PROTCTL[9]) are set, the toggle of incoming data pin can wake-up the system. In order to
receive the incoming data after the system wake-up, the WAKECNT (UUART_PROTCTL[14:11]) shall
be set. These bits field of WAKECNT (UUART_PROCTL[14:11]) indicate how many clock cycle selected
by f
PDS_CNT
do the controller can get the 1st bit (start bit) when the device is wakeup from Power-down
mode. The incoming data wake-wp is shown in Figure 6.13-6.