Registers
1520
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Universal Asynchronous Receiver/Transmitter (UART)
(1)
In the FIFO mode, the receiver data-ready interrupt or receiver time-out interrupt is cleared by the CPU or by the DMA controller,
whichever reads from the receiver FIFO first.
Table 31-11. Interrupt Identification and Interrupt Clearing Information
Priority
Level
IIR Bits
Interrupt Type
Interrupt Source
Event That Clears Interrupt
3
2
1
0
None
0
0
0
1
None
None
None
1
0
1
1
0
Receiver line status
Overrun error, parity error, framing
error, or break is detected.
For an overrun error, reading the line
status register (LSR) clears the
interrupt. For a parity error, framing
error, or break, the interrupt is
cleared only after all the erroneous
data have been read.
2
0
1
0
0
Receiver data-ready
Non-FIFO mode: Receiver data is
ready.
Non-FIFO mode: The receiver buffer
register (RBR) is read.
FIFO mode: Trigger level reached. If
four character times (see
)
pass with no access of the FIFO, the
interrupt is asserted again.
FIFO mode: The FIFO drops below
the trigger level.
(1)
2
1
1
0
0
Receiver time-out
FIFO mode only: No characters have
been removed from or input to the
receiver FIFO during the last four
character times (see
),
and there is at least one character in
the receiver FIFO during this time.
One of the following events:
• A character is read from the
receiver FIFO.
(1)
• A new character arrives in the
receiver FIFO.
• The URRST bit in the power
and emulation management
register (PWREMU_MGMT) is
loaded with 0.
3
0
0
1
0
Transmitter holding
register empty
Non-FIFO mode: Transmitter holding
register (THR) is empty.
FIFO mode: Transmitter FIFO is
empty.
A character is written to the
transmitter holding register (THR) or
the interrupt identification register
(IIR) is read.
31.3.5 FIFO Control Register (FCR)
The FIFO control register (FCR) is a write-only register at the same address as the interrupt identification
register (IIR), which is a read-only register. Use FCR to enable and clear the FIFOs and to select the
receiver FIFO trigger level FCR is shown in
and described in
. The FIFOEN bit
must be set to 1 before other FCR bits are written to or the FCR bits are not programmed.
Access consideration:
IIR and FCR share one address. Regardless of the value of the DLAB bit, reading from the address gives
the content of IIR, and writing to the address modifies FCR.
CAUTION
For proper communication between the UART and the EDMA controller, the
DMAMODE1 bit must be set to 1. Always write a 1 to the DMAMODE1 bit, and
after a hardware reset, change the DMAMODE1 bit from 0 to 1.