TOIM5232

www.vishay.com

Vishay Semiconductors

Rev. 1.3, 04-Jul-12

10

Document Number: 81749

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

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

“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.

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.

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.

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.

Fig. 7 - Data reception with the setting 9.6 kbit/s.

Short RXD pulse

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

1->

T

2->

3->

21031

STA 0

1

1

0

0

0

0

0

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

1->

2->

3->

21032

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

3->

1->

2->

21033

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

1->

2->

3->

21034

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

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

21035