Rainbow Electronics AT91CAP9S250A - Manual (Page 554)

554
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
35.6.5.1 IrDA Modulation
For baud rates up to and including 115.2 Kbits/sec, 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
Table 35-9 .
Figure 35-34 shows an example of character transmission.
Figure 35-34. IrDA Modulation
35.6.5.2 IrDA Baud Rate
Table 35-10 gives some 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.
Table 35-9. IrDA Pulse Duration
Baud Rate Pulse Duration (3/16)
2.4 Kb/s 78.13 µs
9.6 Kb/s 19.53 µs
19.2 Kb/s 9.77 µs
38.4 Kb/s 4.88 µs
57.6 Kb/s 3.26 µs
115.2 Kb/s 1.63 µs
Bit Period Bit Period
3
16
Start
Bit
Data Bits Stop
Bit
0 0 0 0 0 1 1 1 1 1
Transmitter
Output
TXD
Table 35-10. IrDA Baud Rate Error
Peripheral Clock Baud Rate CD Baud Rate Error Pulse Time
3 686 400 115 200 2 0.00% 1.63
20 000 000 115 200 11 1.38% 1.63
32 768 000 115 200 18 1.25% 1.63
40 000 000 115 200 22 1.38% 1.63
3 686 400 57 600 4 0.00% 3.26
20 000 000 57 600 22 1.38% 3.26
32 768 000 57 600 36 1.25% 3.26
40 000 000 57 600 43 0.93% 3.26
3 686 400 38 400 6 0.00% 4.88
20 000 000 38 400 33 1.38% 4.88