UART Interrupts
423
SNIU028A – February 2016 – Revised April 2016
Copyright © 2016, Texas Instruments Incorporated
UART Overview
•
The transmitter transmits each bit for a duration of 8 UART baud clock periods.
•
During the first clock period for a bit, the transmitter shifts the value of that bit onto the SCI_TX pin.
•
The transmitter then holds the current bit value on SCI_TX for 8 UART baud clock periods.
Figure 12-2.
Baud rate setting example:
Baud rate register setting =( F_iclk / (8 * Baud rate)) - 1
(6)
Example: For baud rate of 38400 bps, Baud rate register setting = (15.625 MHz / ( 8 * 38400)) - 1 = 50
Table 12-1.
Desired Baud Rate
UARTHBAUD
UARTMBAUD
UARTLBAUD
110
0
69
91
300
0
25
109
1200
0
6
91
2400
0
3
45
4800
0
1
150
9600
0
0
202
19200
0
0
101
38400
0
0
50
57600
0
0
33
115200
0
0
16
230400
0
0
7
460800
0
0
3
921600
0
0
1
12.3 UART Interrupts
The UART receiver and transmitter can be controlled by interrupts. The receive and transmit interrupts
allow efficient operation of the UART by reading and writing character information to and from the UART
as new data arrives and when old data has just been sent.
The RXRDY flag (UARTRXST.2) used by the receiver indicates that new data is available to be read.
The receiver also has various error interrupts that indicate when a particular error condition is active. An
active error interrupt condition is indicated by the RXERR flag in UARTRXST.
However, the exact source of an error interrupt can be determined by checking the parity error (PE), frame
error (FE), overrun error (OE), break-detect (BRKDT), and wake-up (WAKEUP) flags also located in
UARTRXST.