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NUC126
Aug. 08, 2018
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Rev 1.03
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Case 2 (nCTS transition from high to low):
Power-down mode
CLK
USCIx_CTL0
(nCTS)
stable count
CPU run
WKF
Note1:
Stable count means HCLK source recovery stable count.
Figure 6.20-8 nCTS Wake-Up Case 2
6.20.5.11 Interrupt Events
Protocol Interrupt Events
The following protocol-related events are generated in UART mode and can lead to a protocol
interrupt.
Please note that the bits in register UUART_PROTSTS are not automatically cleared by hardware and
have to be cleared by software in order to monitor new incoming events.
Receiver Line Status
The protocol-related error FRMERR (UUART_PROTSTS[6]) or PARITYERR (UUART_PROTSTS[5])
are two flags that are assigned to each received data word in the corresponding receiver buffer status
registers.
In UART mode, the result of the parity check by the protocol-related error indication (0 = received
parity bit equal to calculated parity value), and the result of frame check by the protocol-related error
indication (0 = received stop bit equal to the format value ‘1’). This information is elaborated for each
data frame.
The break error flag is assigned when the receive data is 0, the received parity and the stop bit are
also 0.
The interrupt indicates that there are parity error, frame error or the break data detection in the
BREAK, FRMERR, PARITYERR (UUART_PROTSTS[7:5]) bits.
Auto Baud Rate Detection
The auto baud rate interrupt, ABRDETIF (UUART_PROTSTS [9]), indicate that the timing
measurement counter has getting 2-bit duration for auto baud rate capture function.
The auto baud rate detection function will be enabled in the first falling edge of receiver signal. The
auto baud rate detection function is measurement after the next following falling is detected and it is
finished when the frame transfer done. After the transfer done, the timing measurement counter value
divided by twice is equal to the number of sample time per bit. The user can read the value of
BRDETITV (UUART_PROTCTL[24:16]) and write into the baud rate generator register CLKDIV
(UUART_BRGEN[25:16]).
Data Transfer Interrupt Handling
The data transfer interrupts indicate events related to UART frame handling.
Transmit start interrupt:
Bit TXSTIF (UUART_PROTSTS [1]) is set after the start bit of a data word. In buffer
mode, this is the earliest point in time when a new data word can be written to
UUART_TXDAT.
Transmitter finished: