Silan

Semiconductors

SC5272

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

Rev: 1.0

2000.12.31

6

2. IR OPERATION

In the IR Type of operation, the functions are similar to the above descriptions except that the output waveform

carried by SC5262-IR has a frequency of 38kHz. Details are as follows.

Code Bits

The Code Bits are further modulated with a 38kHz carrier frequency and can be”0”,”1” or “ f ” bit. Their waveform

are shown below:

OSC

"0"

"1"

"f"

Sync

160

λ

20

λ

60

λ

Note:

λ=2 clock lengths

620

λ

Code Word

A Code Word is made up of code bits and the format is the same as that of the RF Code Word.

Code Frame

Likewise, a Code Frame is made up of Code Words and the format is the same as that of RF type of operation.

Oscillator

The SC5262-IR is specially designed for infrared remote control applications and its output waveform carries

38kHz frequency. To get the 38kHz carrier frequency at the data output, the oscillator frequency must be 76kHz.

A 440k

Ω resistor connected between OSC1 and OSC2 pins of SC5262-IR is recommended. Moreover, for a

matching decoder frequency, 1M

Ω resistor connected between the OSC1 and OSC2 pins of SC5272 is also

recommended.

3.VALID TRANSMISSION

When the SC5272 receives a transmission code word, it initially checks whether this is a valid transmission. For

a transmission to be valid, (1) it must be a complete code word, and (2) the address bits must match the address

setting at the address pins. After two consecutive valid transmission, SC5272 (1) drives the data pins according to

the data bits received, and (2) rise VT to high voltage(high state).

The timings are shown in the following diagram.

1st word

2nd word

Sync bit

Sync bit

Ta

Tb

Tc

Din

Data pins

(momentary)

VT

Ta= 8 OSC clock width

Tb= 1 OSC clock width

Tc=2 code word width