Start-bit
5, 6, 7, or 8 bits of data according to LCR register
Parity bit
(see LCR
register)
1 or 2
stop-bits
according
to LCR
register
uart-005
Public Version
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UART/IrDA/CIR Environment
The UART module is functionally compatible with the TL16C750 UART and earlier designs such as the
TL16C550.
shows the UART frame data format.
Figure 19-5. UART Frame Data Format
19.2.5 IrDA Functional Interfaces
19.2.5.1 UART3 Interface Description
describes the UART3 interface.
Table 19-4. UART3 I/O Description
Signal
I/O
(1)
Description
Reset
IrDA Signals
uart3_rx_irrx
I
Serial data input
Unknown
uart3_tx_irtx
O
Serial data output in IrDA modes (SIR, MIR, and FIR). In other
0
(2)
modes, this pin is set to the reset value (inactive state).
uart3_rts_sd
O
SD mode is used to configure the transceivers.
1
The SD pinout is an inverted value of the
UART3.
[6] SD_MOD bit.
(1)
I = Input, O = Output
(2)
This value is only for IrDA mode. It is not for UART and CIR modes.
19.2.5.2 IrDA Protocol and Data Format
19.2.5.2.1 SIR Mode
In SIR mode, data is transferred between the MPU and peripheral devices at speeds of up to 115,200
baud. A SIR transmit frame begins with start flags (a single 0xC0, a multiple 0xC0, or a single 0xC0
preceded by a number of 0xFF flags), is followed by frame data and a CRC-16, and ends with a stop flag
(0xC1).
The bit format for a single word uses 1 start bit, 8 data bits, and 1 stop bit, and is unaffected by the use
and settings of the UART3.
register.
The UART3.
[6] XBOF_TYPE bit selects whether the 0xC0 or 0xFF start patterns are used when
multiple start flags are required.
The SIR transmit state-machine attaches start flags, CRC-16, and stop flags, and checks the outgoing
data to establish whether 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 start flags is about to be transmitted, the SIR state-machine first sends an escape
character (0x7D), then inverts the fifth bit of the real data to be sent, and sends this data immediately after
the 0x7D character.
2875
SWPU177N – December 2009 – Revised November 2010
UART/IrDA/CIR
Copyright © 2009–2010, Texas Instruments Incorporated