Datasheet HT12D, HT12F (Holtek) - 4

HT12D/HT12F Functional Description Operation Flowchart
The 212 series of decoders provides various combina- The oscillator is disabled in the standby state and acti- tions of addresses and data pins in different packages vated when a logic ²high² signal applies to the DIN pin. so as to pair with the 212 series of encoders. That is to say, the DIN should be kept low if there is no The decoders receive data that are transmitted by an signal input. encoder and interpret the first N bits of code period as P o w e r o n 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- S t a n d b y m o d e dress and data. The decoders will then check the re- ceived address three times continuously. If the received D i s a b l e V T & address codes all match the contents of the decoder¢s N o C o d e i n ? i g n o r e t h e r e s t o f local address, the 12-N bits of data are decoded to acti- t h i s w o r d vate the output pins and the VT pin is set high to indicate Y e s a valid transmission. This will last unless the address code is incorrect or no signal is received. A d d r e s s b i t s N o m a t c h e d ? The output of the VT pin is high only when the transmis- sion is valid. Otherwise it is always low. Y e s
Output Type
S t o r e d a t a Of the 212 series of decoders, the HT12F has no data output pin but its VT pin can be used as a momentary M a t c h N o data output. The HT12D, on the other hand, provides 4 p r e v i o u s s t o r e d d a t a ? latch type data pins whose data remain unchanged until Y e s new data are received.
Part Data Address Output Operating
N o 3 t i m e s o f c h e c k i n g
No. Pins Pins Type Voltage
c o m p l e t e d ? HT12D 4 8 Latch 2.4V~12V Y e s HT12F 0 12 ¾ 2.4V~12V 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 N o A d d r e s s o r d a t a e r r o r ? Y e s
Decoder Timing
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 < 1 w o r d E n c o d e r D O U T 4 w o r d s T r a n s m i t t e d 4 w o r d s C o n t i n u o u s l y 2 1 4 c l o c k s 2 1 4 c l o c k s D e c o d e r V T c h e c k c h e c k L a t c h e d D a t a O u t Rev. 1.20 4 February 20, 2009 Document Outline Features Applications General Description Selection Table Block Diagram Pin Assignment Pin Description Absolute Maximum Ratings Electrical Characteristics Functional Description Application Circuits Package Information Product Tape and Reel Specifications