LM3S5656 Datasheet, PDF (617/1140 Pages) Texas Instruments – Stellaris® LM3S5656 Microcontroller

Stellaris^® LM3S5656 Microcontroller
Figure 13-3. IrDA Data Modulation
UnTx
Start
bit
0
1
Data bits
0
1
0
0
UnTx with IrDA
UnRx with IrDA
Bit period
1
1
Stop
bit
0
1
3
16
Bit period
UnRx
0
1
Start
0
1
0
0
Data bits
1
1
0
1
Stop
13.3.5
13.3.6
In both normal and low-power IrDA modes:
■ During transmission, the UART data bit is used as the base for encoding
■ During reception, the decoded bits are transferred to the UART receive logic
The IrDA SIR physical layer specifies a half-duplex communication link, with a minimum 10-ms
delay between transmission and reception. This delay must be generated by software because it
is not automatically supported by the UART. The delay is required because the infrared receiver
electronics might become biased or even saturated from the optical power coupled from the adjacent
transmitter LED. This delay is known as latency or receiver setup time.
ISO 7816 Support
The UART offers basic support to allow communication with an ISO 7816 smartcard. When bit 3
(SMART) of the UARTCTL register is set, the UnTx signal is used as a bit clock, and the UnRx signal
is used as the half-duplex communication line connected to the smartcard. A GPIO signal can be
used to generate the reset signal to the smartcard. The remaining smartcard signals should be
provided by the system design. The maximum clock rate in this mode is system clock / 16.
When using ISO 7816 mode, the UARTLCRH register must be set to transmit 8-bit words (WLEN
bits 6:5 configured to 0x3) with EVEN parity (PEN set and EPS set). In this mode, the UART
automatically uses 2 stop bits, and the STP2 bit of the UARTLCRH register is ignored.
If a parity error is detected during transmission, UnRx is pulled Low during the second stop bit. In
this case, the UART aborts the transmission, flushes the transmit FIFO and discards any data it
contains, and raises a parity error interrupt, allowing software to detect the problem and initiate
retransmission of the affected data. Note that the UART does not support automatic retransmission
in this case.
LIN Support
The UART module offers hardware support for the LIN protocol as either a master or a slave. The
LIN mode is enabled by setting the LIN bit in the UARTCTL register. A LIN message is identified
by the use of a Sync Break at the beginning of the message. The Sync Break is a transmission of
a series of 0s. The Sync Break is followed by the Sync data field (0x55). Figure 13-4 on page 618
illustrates the structure of a LIN message.
January 21, 2012
617
Texas Instruments-Production Data