48 MHz
14 bits divisor:
1/(DLH,DLL)
DLH
DLL
16x 13x divisor
MDR1[2:0]
MODE_SELECT bit field
UART MODE 16x
UART MODE 13x
TX UART clock
RX UART clock
uart-032
Start
bit
5, 6, 7 or 8 bits of data according to
LCR register
Parity
bit,
see LCR
register
1 or 2
stop bit
according
to LCR
register
Functional Description
The module can be placed in an alternate mode (FIFO mode) to relieve the processor of excessive
software overhead by buffering received/transmitted characters.
Both the receiver and transmitter FIFOs can store up to 64 bytes of data (plus three additional bits of error
status per byte for the receiver FIFO) and have selectable trigger levels. Both interrupts and DMA are
available to control the data flow between the LH and the module.
19.3.8.1 UART Mode
The UART uses a wired interface for serial communication with a remote device.
The UART module is functionally compatible with the TL16C750 UART and is also functionally compatible
to earlier designs, such as the TL16C550. The UART module can use hardware or software flow control to
manage transmission and reception. Hardware flow control significantly reduces software overhead and
increases system efficiency by automatically controlling serial data flow using the RTS output and CTS
input signals. Software flow control automatically controls data flow by using programmable XON/XOFF
characters.
The UART modem module is enhanced with an autobauding functionality which in control mode allows to
automatically set the speed, the number of bit per character, the parity selected.
Figure 19-14. UART Data Format
19.3.8.1.1 UART Clock Generation: Baud Rate Generation
The UART function contains a programmable baud generator and a set of fixed dividers that divide the 48-
MHz clock input down to the expected baud rate.
shows the baud rate generator and associated controls.
Figure 19-15. Baud Rate Generation
CAUTION
Before initializing or modifying clock parameter controls (UARTi.UART_DLH,
UARTi.UART_DLL), MODE_SELECT = DISABLE (UARTi.UART_MDR1[2:0])
must be set to 0x7. Failure to observe this rule can result in unpredictable
module behavior.
3474
Universal Asynchronous Receiver/Transmitter (UART)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated