at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 289

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

IrDA Demodulator
Figure 113. IrDA Demodulator Operations
1790A–ATARM–11/03
Receiver
Counter
Value
Input
MCK
RXD
6
5
4
Rejected
Pulse
Table 52. IrDA Baud Rate Error
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 113 illustrates the operations of the IrDA demodulator.
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.
3
Peripheral Clock
40 000 000
3 686 400
20 000 000
32 768 000
40 000 000
3 686 400
20 000 000
32 768 000
40 000 000
3 686 400
20 000 000
32 768 000
2
6
6
5
Baud rate
38 400
19 200
19 200
19 200
19 200
9 600
9 600
9 600
9 600
2 400
2 400
2 400
4
3
2
1
0
CD
65
12
65
107
130
24
130
213
260
96
521
853
Accepted
Pulse
Driven Low During 16 Baud Rate Clock Cycles
Baud rate Error
0.16%
0.00%
0.16%
0.31%
0.16%
0.00%
0.16%
0.16%
0.16%
0.00%
0.03%
0.04%
AT91RM3400
Pulse time
4.88
9.77
9.77
9.77
9.77
19.53
19.53
19.53
19.53
78.13
78.13
78.13
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