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M0A21/M0A23 Series
May 06, 2022
Page
425
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
start
bit 1
bit 2
bit 0
bit 3
bit 4
bit 5
bit 6
UART_RX
0 1 2 3
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bit 7
parity
stop
Auto Baud
Rate Counter
m
m÷ 2
n
keep old BRD
n = 00
n = 01
n = 10
n = 11
ABRDIF
(UART_FIFOSTS[1])
BRD
(UART_BAUD[15:0])
ABRDEN
(UART_ALTCTL[18])
n = ABRDBITS (UART_ALTCTL[20:19])
Figure 6.11-3 Auto-Baud Rate Measurement
6.11.5.3 Programming Sequence Example
1. Program ABRDBITS (UART_ALTCTL[20:19]) to determines 2
ABRDBITS
bit time from UART RX
receive START bit falling edge to data 1st rising edge.
2. Set ABRIEN (UART_INTEN[18]) to enable auto-baud rate function interrupt.
3. Set ABRDEN (UART_ALTCTL[18]) to enable auto-baud rate function.
4. ABRDIF (UART_FIFOSTS[1]) is set, the auto-baud rate measurement is finished.
5. Operate UART transmit and receive action.
6. ABRDTOIF (UART_FIFOSTS[2]) is set, if auto-baud rate counter is overflow.
7. Go to Step 3.
6.11.5.4 UART Controller Transmit Delay Time Value
The UART controller programs DLY (UART_TOUT[15:8]) to control the transfer delay time between the
last stop bit and next start bit in transmission. The unit is baud. The operation is shown in Figure 6.11-4.
Start
TX
Byte (i)
Byte (i+1)
Stop
DLY
Start
Figure 6.11-4 Transmit Delay Time Operation
6.11.5.5 UART Controller FIFO Control and Status
The UART controller is built-in with a 16 bytes transmitter FIFO (TX_FIFO) and a 16 bytes receiver FIFO
(RX_FIFO) that reduces the number of interrupts presented to the CPU. The CPU can read the status
of the UART at any time during operation. The reported status information includes condition of the
transfer operations being performed by the UART, as well as 3 error conditions (parity error, framing
error, break interrupt) occur if receiving data has parity, frame or break error. UART, IrDA, LIN and RS-
485 mode support FIFO control and status function.