Silan

Semiconductors

SC2268

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

Rev: 1.0

2000.12.31

3

FUNCTIONAL DESCRIPTION

1. KEY INPUT

Up to eight keys can be directly connected to pins I1 ~

I8. Please refer to the diagram right.

Furthermore, SC2268 has a buit-in pull-low resistor of

about 60K ~ 110K

Ω which reduces the need for

external components.

1

2

3

4

5

6

7

8

SC2268

I1

I2

I3

I4

I5

I6

I7

I8

Vcc

2. OSCILLATOR

An oscillation circuit can be constructed using the

CMOS inverter and Built-in Feedback resistor, 455kHz

crystal and two 220pf capacitors. The carrier frequency

is 38kHz.

Unless any of the 8 keys (I1~I8) is being operated,

the oscillation is automatically stopped. Thus, power

consumption is considerably reduced.

OSCI

455kHz

OSCO

220pf

220pf

SC2268

15

14

3. TRANMISSION WAVEFORM

When any of the 8 keys (I1 ~ I8) is set to “High”, the TxOUT outputs one start word followed by 2 identical

data words and a space. The code will be continuously outputted until the key is released. If for any

reason, the key was released during the code transmission process, the code that is being transmitted

during the key release action will still be completely outputted. Please refer to the following diagram.

Start

Word

Data

Word

Data

Word

Space

Start

Word

Data

Word

Data

Word

Space

Start

Word

Data

Word

Data

Word

Space

20ms

80ms

1 Frame = 80ms

I1 ~ I8

Tx OUT

*OSC = 455kHz