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HT6230

Infrared Remote Encoder

Holtek Semiconductor 

HT6230

Functional Description

Key operation

When MS is low, the legal key operation is that

only one ZIN or XIN can be connected to one

DRS driver and if more than one XIN, ZIN or

both are pressed at the same time then the key

operation is recognized as illegal; hence, the os-

cillator will not start. When MS is high, the le-

gal key operation is that exactly one ZIN and

one XIN are connected to two DRS drivers and

other cases of key operation are all considered

as illegal.

However, when one XIN or ZIN is connected to

more than one DRS, the last key scan driver is

to generate output data code.

Format of transmission code

The output pin CODE transmits the data code

as a code format, as shown at the bottom figure.

The method of transmitting one code bit is called

biphase transmission and is represented by the

following fig:

lo g ic 0

lo g ic 1

Where one code bit time is 3´28´TOSC. The out-

put signal of the MCODE pin is the signal of the

generated output code modulated by 1/12 of the

system frequency with 1/4 duty cycle. In quies-

cent state both CODE and MCODE are high

impedance.

Key scan drivers

The key scan drivers DRS0 to DRS7 are open

drain NMOS and the outputs of these are all

low in quiescent state. When a legal key opera-

tion is detected, the debounce cycle starts and

at the end of the debounce cycle, the DRS out-

puts are high impedance. Furthermore, the

scanning cycle starts and DRS outputs take

turns to switch to low state.

Programmable output data code

The output data code corresponding to each key

is programmable by hardware mask option.

The PAL circuit is necessary for this purpose.

Operation mode

· One-key system mode

The device enters this mode by switching the

MS input pin to low state. The pull-high resis-

tors are connected to all XIN and ZIN inputs

so that all sense inputs are at high state, until

pulled to low state by key operation. In this

mode the legal key operation is that only one

ZIN or XIN can be connected to one DRS.

When a sense input detects a low level, an en-

able signal is generated to latch the system or

command latches. If the sense input belongs

to ZIN, the corresponding system code is gen-

erated and the command code is defined as all

one code

1

1

M SB

LS B M S B

LS B

D e b o u n c e c y c le

S can

( 1 6 b it- tim e )

c y c le

s ta rt

S ta rt

b its

C o n tro l

b it

5 s y s te m b its

6 c o m m a n d b its

C ode 1

1 6 b it- tim e

s ta rt

4 8 b it- tim e

R e p e titio n tim e ( 6 4 b it- tim e )

C ode 2

1 6 b it- tim e

Transmission code format

5

April 19, 2000

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