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ATSAM4S-XPLD
716
SAM4S [DATASHEET]
11100E–ATARM–24-Jul-13
35.7.5.3 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.
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 35-35.IrDA Demodulator Operations
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.
value higher than 0 in order to assure IrDA communications operate correctly.
20 000 000
38 400
33
1.38%
4.88
32 768 000
38 400
53
0.63%
4.88
40 000 000
38 400
65
0.16%
4.88
3 686 400
19 200
12
0.00%
9.77
20 000 000
19 200
65
0.16%
9.77
32 768 000
19 200
107
0.31%
9.77
40 000 000
19 200
130
0.16%
9.77
3 686 400
9 600
24
0.00%
19.53
20 000 000
9 600
130
0.16%
19.53
32 768 000
9 600
213
0.16%
19.53
40 000 000
9 600
260
0.16%
19.53
3 686 400
2 400
96
0.00%
78.13
20 000 000
2 400
521
0.03%
78.13
32 768 000
2 400
853
0.04%
78.13
Table 35-13. IrDA Baud Rate Error (Continued)
Peripheral Clock
Baud Rate
CD
Baud Rate Error
Pulse Time
MCK
RXD
Receiver
Input
Pulse
Rejected
6
5
4
3
2
6
1
6
5
4
3
2
0
Pulse
Accepted
Counter
Value