Decoder timing

HT12D/HT12F

Rev. 1.10

4

November 18, 2002

Functional Description

Operation

The 2

tions of addresses and data pins in different packages

so as to pair with the 2

The decoders receive data that are transmitted by an

encoder and interpret the first N bits of code period as

addresses and the last 12

-N bits as data, where N is the

address code number. A signal on the DIN pin activates

the oscillator which in turn decodes the incoming ad-

dress and data. The decoders will then check the re-

ceived address three times continuously. If the received

address codes all match the contents of the decoder

¢s

local address, the 12

-N bits of data are decoded to acti-

vate the output pins and the VT pin is set high to indicate

a valid transmission. This will last unless the address

code is incorrect or no signal is received.

The output of the VT pin is high only when the transmis-

sion is valid. Otherwise it is always low.

Output type

Of the 2

output pin but its VT pin can be used as a momentary

data output. The HT12D, on the other hand, provides 4

latch type data pins whose data remain unchanged until

new data are received.

Part

No.

Data

Pins

Address

Pins

Output

Type

Operating

Voltage

HT12D

4

8

Latch

2.4V~12V

HT12F

0

12

¾

2.4V~12V

Flowchart

The oscillator is disabled in the standby state and acti-

vated when a logic

²high² signal applies to the DIN pin.

That is to say, the DIN should be kept low if there is no

signal input.

Y e s

C o d e i n ?

S t o r e d a t a

N o

Y e s

N o

N o

N o

Y e s

S t a n d b y m o d e

D i s a b l e V T &

i g n o r e t h e r e s t o f

t h i s w o r d

Y e s

N o

Y e s

A d d r e s s o r

d a t a e r r o r ?

L a t c h d a t a

t o o u t p u t &

a c t i v a t e V T

A d d r e s s b i t s

m a t c h e d ?

M a t c h

p r e v i o u s s t o r e d

d a t a ?

P o w e r o n

3 t i m e s

o f c h e c k i n g

c o m p l e t e d ?

2

c l o c k s

1 4

c h e c k

4 w o r d s

4 w o r d s

E n c o d e r

D O U T

T r a n s m i t t e d

C o n t i n u o u s l y

< 1 w o r d

E n c o d e r

T r a n s m i s s i o n

E n a b l e

c h e c k

D e c o d e r V T

L a t c h e d

D a t a O u t

2

c l o c k s

1 4