4
DEMO MANUAL DC112A
OPERATIO
U
IrDA-SIR
Because SIR systems transmit a pulse for a zero and
nothing for a one (see Figure 3a), the two photographs
demonstrating the SIR modulation show a sequence of
zeros. In both photographs, the input data to the transmit-
ter is shown on the bottom and the output of the IR receiver
is shown on the top. Note that the receiver output is a TTL
LOW for a transmitted light pulse. The two photos, Figures
3b and 3c, show received data at 1 meter and 1cm. There
is not much difference at distances in between.
0
1
0
0
1
1
0
1
0
1328 F02a
NRZ DATA
IrDA-SIR HIGH = LIGHT TRANSMITTED
DATA RATES: 2400BAUD TO 115kBAUD
BIT INTERVAL: 417
µ
s TO 8.7
µ
s
PULSE WIDTH: 3/16 OF INTERVAL OR 1.63
µ
s
TRANSMITTER
INPUT
RECEIVER
OUTPUT
RECEIVER
OUTPUT
TRANSMITTER
INPUT
IrDA-SIR (1m)
IrDA-SIR (1cm)
Figure 3. IrDA-SIR Modulation
3b
3c
3a
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