TOIM5232 Datasheet, PDF (10/13 Pages) Vishay Siliconix – SIR Endec for IrDA® Applications Integrated Interface Circuit

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TRANSMIT (TXD) CHANNEL
Figure 4 shows the transmission in the default mode. For
data transfer, the endec is set to that mode by BR/D = “0”.
In the examples “6” is always transmitted (binary
1->
“00000110”). The “0” is represented in the IrDA protocol by
an optical pulse. Also here the LSB is transmitted first after
the start bit. “1” is not transmitted.
2->
TOIM5232
Vishay Semiconductors
STA 0 1 1 0 0 0 0 0
1->
2->
T
3->
1) Ch1: TD_232 inp. pin 4, vertical scale: 2 V/div., horizontal scale: 200 µs/div.
2) Ch2: TD_IR, pin 14; 1.6 µs pulse duration
3) Ch3: TD_LED, pin 9
21031
Fig. 4 - Data transmission with 9.6 kbit/s,1.627 μs pulse duration
Channel 1 shows the signal from the RS232 port already
converted to 3 V logic by U1. The Endec encodes that signal
to the RZI IrDA format where a “0” is represented by a pulse.
That is the trace of channel 2. This output is connected the
TXD input of the transceiver and this signal is transmitted as
optical output signal. Channel 3 is the signal for an indicator
lamp connected to the TD_LED driver output. Use 180 
serial resistor to supply voltage for limiting the current
through the LED (not shown in the circuit diagram).
When using the (not recommended) 3/16-bit pulse width the
oscillogram looks like figure 5.
3->
1) Ch1: TD_232, pin 4, vertical scale: 2 V/div., horizontal scale: 20 µs/div.
2) Ch2: TD_IR, pin 14; 1.6 µs pulse duration
3) Ch3: TD_LED, pin 9
21033
Fig. 6 - Data transmission with the setting 115.2 kbit/s, 1.627 μs
pulse duration. By definition, the pulse duration of 1.627 μs is
identical to the 3/16-bit pulse width.
RECEIVE (RXD) CHANNEL
In the default 9600 bit/s mode the signals will look like those
shown in figure 7 and figure 8.
1->
2->
3->
1) Ch1: TOIM4232; RD_IR, pin 15, vertical scale: 2 V/div.,
horizontal scale: 200 µs/div.
2) Ch2: TOIM4232; RD_232, pin 3
3) Ch3: TOIM4232; RD_LED, pin 10
21034
Fig. 7 - Data reception with the setting 9.6 kbit/s.
Short RXD pulse
1->
1->
2->
2->
3->
1) Ch1: TD_232, pin 4, vertical scale: 2 V/div., horizontal scale: 200 µs/div.
2) Ch2: TD_IR, pin 14; 3/16 bit pulse duration
3) Ch3: TD_LED, pin 9
21032
Fig. 5 - Data transmission with the setting 9.6 kbit/s,
3/16 bit pulse duration (19.5 μs)
The transmission with the highest SIR bit rate of 115.2 bit/s
looks like what is shown in figure 6. However, the horizontal
time scale is different.
3->
1) Ch1: TOIM4232; RD_IR, pin 15, vertical scale: 2 V/div.,
horizontal scale: 200 µs/div.
2) Ch2: TOIM4232; RD_232, pin 3
3) Ch3: TOIM4232; RD_LED, pin 10
21035
Fig. 8 - Data reception with the setting 9.6 kbit/s.
Same as in figure 7, extended pulse duration
The endec stretches the received pulses of about 2 µs
duration from the transceiver output (figure 7, channel 1)
independent of the pulse duration to the full bit width
generating NRZ code (channel 2). Channel 3 is the signal for
the indicator lamp.
As shown in figure 8, channels 2 and 3, the final NRZ signal
is identical to figure 7, even when longer pulses are received.
In the 115.2 kbit/s mode the signals will look like those shown
Rev. 1.3, 04-Jul-12
10
Document Number: 81749
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