Datasheet

The IrDA mode is enabled by writing the value 0x8 to US_MR.USART_MODE. The IrDA Filter register (US_IF) is
used to configure the demodulator filter
. The USART transmitter and receiver operate in a normal Asynchronous
mode and all parameters are accessible. Note that the modulator and the demodulator are activated.
Figure 46-32. Connection to IrDA Transceivers
IrDA
Transceivers
RXD RX
TXD
TX
USART
Demodulator
Modulator
Receiver
Transmitter
The receiver and the transmitter must be enabled or disabled depending on the direction of the transmission to be
managed.
T
o receive IrDA signals, the following needs to be done:
• Disable TX and Enable RX
• Configure the TXD pin as PIO and set it as an output to 0 (to avoid LED emission). Disable the internal pull-up
(better for power consumption).
• Receive data
46.6.5.1 IrDA Modulation
For baud rates up to and including 115.2 kbit/s, the RZI modulation scheme is used. “0” is represented by a light
pulse of 3/16th of a bit time. Some examples of signal pulse duration are shown in the following table.
Table 46-9. IrDA Pulse Duration
Baud Rate Pulse Duration (3/16)
2.4 kbit/s 78.13 μs
9.6 kbit/s 19.53 μs
19.2 kbit/s 9.77 μs
38.4 kbit/s 4.88 μs
57.6 kbit/s 3.26 μs
115.2 kbit/s 1.63 μs
The following figure shows an example of character transmission.
Figure 46-33. IrDA Modulation
Bit Period
3/16 Bit Period
Start
Bit
Data Bits
Stop
Bit
0 00 0 0
1 11 11
Transmitter
Output
TXD
46.6.5.2 IrDA Baud Rate
The following table provides examples of CD values, baud rate error, and pulse duration. Note that the requirement
on the maximum acceptable error of ±1.87% must be met.
SAM E70/S70/V70/V71 Family
Universal Synchronous Asynchronous Receiver T
ransc...
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echnology Inc.
Datasheet
DS60001527D-page 1201