N * 8 bits
8bits
M * 8 bits
2 * 8 bits
8bits
xBOF
BOF
A
C
I
CRC
EOF
FIFO DATA
8bits
8bits
Functional Description
3. Take a guard time according to stop-bit definition.
4. Set the BREAK_EN bit to 1.
The break condition is asserted while the BREAK_EN bit is set to 1.
The time-out counter and break condition apply only to UART modem operation and not to IrDA/CIR mode
operation.
19.3.8.2 IrDA Mode
19.3.8.2.1 SIR Mode
In slow infrared (SIR) mode, data transfers take place between the LH and peripheral devices at speeds of
up to 115200 bauds. A SIR transmit frame starts with start flags (either a single 0xC0, multiple 0xC0, or a
single 0xC0 preceded by a number of 0xFF flags), followed by frame data, CRC-16, and ends with a stop
flag (0xC1). The bit format for a single word uses a single start bit, eight data bits, and one stop bit. The
format is unaffected by the use and settings of the LCR register.
Note that BLR[6] is used to select whether to use 0xC0 or 0xFF start patterns when multiple start flags are
required.
The SIR transmit state machine attaches start flags, CRC-16, and stop flags. It checks the outgoing data
to establish if data transparency is required.
SIR transparency is carried out if the outgoing data, between the start and stop flags, contains 0xC0,
0xC1, or 0x7D. If one of these is about to be transmitted, then the SIR state machine sends an escape
character (0x7D) first, then inverts the fifth bit of the real data to be sent and sends this data immediately
after the 0x7D character.
The SIR receive state machine recovers the receive clock, removes the start flags, removes any
transparency from the incoming data, and determines frame boundary with reception of the stop flag. It
also checks for errors, such as frame abort (0x7D character followed immediately by a 0xC1 stop flag,
without transparency), CRC error, and frame-length error. At the end of a frame reception, the LH reads
the line status register (LSR) to find out possible errors of the received frame.
Data can be transferred both ways by the module, but when the device is transmitting the IR RX circuitry
is automatically disabled by hardware. See bit 5 in
, Auxiliary Control Register, for a
description of the logical operation. Note: This applies to all three modes SIR, MIR, and FIR.
The infrared output in SIR mode can either be 1.6
μ
s or 3/16 encoding, selected by the PULSETYPE bit of
the Auxiliary Control Register (ACREG[7]). In 1.6
μ
s encoding, the infrared pulse width is 1.6
μ
s and in 3/16
encoding the infrared pulse width is 3/16 of a bit duration (1/baud-rate). The receiver supports both 3/16
and 1.6
μ
s pulse duration by default. The transmitting device must send at least two start flags at the start
of each frame for back-to-back frames. Note: Reception supports variable-length stop bits.
19.3.8.2.1.1 Frame Format
Figure 19-16. IrDA SIR Frame Format
The CRC is applied on the address (A), control (C) and information (I) bytes.
Note: The two words of CRC are written in the FIFO in reception.
3480
Universal Asynchronous Receiver/Transmitter (UART)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated