HT6240-002

7

December 16, 1999

Clock oscillating circuit

HT6240 has built-in feedback resistor and

CMOS inverter, so a ceramic resonator can con-

nect between the oscillator circuit input pin

(OSCI) and the output pin (OSCO), (see Fig. 3).

When the ceramic resonator is set to 455kHz,

the carrier can be set 38kHz.

The oscillating circuit will stop when there is no

key pressed to save power dissipation.

Transmission code

When the resonator is 455kHz, the carrier of

the transmission signal is 38kHz. One pulse

width is 0.53ms. Therefore, twenty 38kHz

clocks are included in the 0.53ms pulse width.

(Fig.4 shows the carrier)

HT6240-002 has two different formats. When

the custom code is equal to zero, CT will send

the 1st format. Otherwise, it will send the 2nd

format.

If the custom code (C0~C7) is ²0000 0000² then

Fig. 5 shows the formation of the transmission

code. Fig. 6 shows the transmission code ²0²

and ²1² and pulse width. Fig. 7 shows the for-

mation of the 1-word transmission code. If a le-

gal key is pressed, HT6240-002 will send at

least five words (see Fig. 8).

N o t e : T h e se c apac i t o r s d e pend on t he r e sonat or s.

U se t h e v a l ues r ec om m ende d by t h e r e sonat or

m anuf ac t u r e r .

O S CI

O S CO

H T 6240- 002

Fig. 3

8. 8m s

26. 4m s

0. 53 m s

Fig. 4 Carrier

0. 53 m s

2. 11 m s

0. 53 m s

4. 22 m s

B i t " 0 "

B i t " 1 "

Fig. 6 Transmission code ²0² and ²1² and

pulse width of HT6240-002

D0

D1

D2

D3

D4

D5

D a t a c ode

Fig. 5 Formation of the transmission code