SAM7X256_14 Datasheet, PDF (314/662 Pages) ATMEL Corporation – ARM-based Flash MCU

30.6.5.3 IrDA Demodulator
The demodulator is based on the IrDA Receive filter comprised of an 8-bit down counter which is loaded with the value
programmed in US_IF. When a falling edge is detected on the RXD pin, the Filter Counter starts counting down at the
Master Clock (MCK) speed. If a rising edge is detected on the RXD pin, the counter stops and is reloaded with US_IF. If
no rising edge is detected when the counter reaches 0, the input of the receiver is driven low during one bit time.
Figure 30-25 illustrates the operations of the IrDA demodulator.
Figure 30-25. IrDA Demodulator Operations
MCK
RXD
Counter
Value
Receiver
Input
65432 6
Pulse
Rejected
6543210
Pulse
Accepted
As the IrDA mode uses the same logic as the ISO7816, note that the FI_DI_RATIO field in US_FIDI must be set to a
value higher than 0 in order to assure IrDA communications operate correctly.
SAM7X Series [DATASHEET]
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