Peripheral Architecture
1506
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Universal Asynchronous Receiver/Transmitter (UART)
31.2.2 Signal Descriptions
The UARTs utilize a minimal number of signal connections to interface with external devices. The UART
signal descriptions are included in
. Note that the number of UARTs and their supported
features vary on each device, see your device-specific data manual for more details.
(1)
The value
n
indicates the applicable UART; that is, UART0, UART1, etc.
(2)
This signal is not supported in all UARTs. See your device-specific data manual to check if it is
supported.
Table 31-3. UART Signal Descriptions
Signal Name
(1)
Signal Type
Function
UARTn_TXD
Output
Serial data transmit
UARTn_RXD
Input
Serial data receive
UARTn_CTS
(2)
Input
Clear-to-Send handshaking signal
UARTn_RTS
(2)
Output
Request-to-Send handshaking signal
31.2.3 Pin Multiplexing
Extensive pin multiplexing is used to accommodate the largest number of peripheral functions in the
smallest possible package. Pin multiplexing is controlled using a combination of hardware configuration at
device reset and software programmable register settings. See your device-specific data manual to
determine how pin multiplexing affects the UART.
31.2.4 Protocol Description
31.2.4.1 Transmission
The UART transmitter section includes a transmitter hold register (THR) and a transmitter shift register
(TSR). When the UART is in the FIFO mode, THR is a 16-byte FIFO. Transmitter section control is a
function of the UART line control register (LCR). Based on the settings chosen in LCR, the UART
transmitter sends the following to the receiving device:
•
1 START bit
•
5, 6, 7, or 8 data bits
•
1 PARITY bit (optional)
•
1, 1.5, or 2 STOP bits
31.2.4.2 Reception
The UART receiver section includes a receiver shift register (RSR) and a receiver buffer register (RBR).
When the UART is in the FIFO mode, RBR is a 16-byte FIFO. Receiver section control is a function of the
UART line control register (LCR). Based on the settings chosen in LCR, the UART receiver accepts the
following from the transmitting device:
•
1 START bit
•
5, 6, 7, or 8 data bits
•
1 PARITY bit (optional)
•
1 STOP bit (any other STOP bits transferred with the above data are not detected)