HT12A/HT12EFunctional DescriptionOperation The 212 series of encoders begin a 4-word transmission cycle upon receipt of a transmission enable (TE for the HT12E or D8~D11 for the HT12A, active low). This cycle will repeat itself as long as the transmission enable (TE or D8~D11) is held low. Once the transmission enable returns high the encoder output completes its final cycle and then stops as shown below. T 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 Transmission timing for the HT12E D 8 ~ D 1 1 K e y - i n < 1 w o r d E n c o d e r D O U T w i t h 3 8 k H z c a r r i e r 1 w o r d 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 Transmission timing for the HT12A (L/M=Floating or VDD) D 8 ~ D 1 1 K e y - i n ( a l d a t a = 1 ) < 1 w o r d 7 w o r d s E n c o d e r D O U T 7 w o r d s 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 1 w o r d ( a l d a t a = 1 ) Transmission timing for the HT12A (L/M=VSS) Information Word If L/M=1 the device is in the latch mode (for use with the latch type of data decoders). When the transmission enable is re- moved during a transmission, the DOUT pin outputs a complete word and then stops. On the other hand, if L/M=0 the de- vice is in the momentary mode (for use with the momentary type of data decoders). When the transmission enable is removed during a transmission, the DOUT outputs a complete word and then adds 7 words all with the ²1² data code. An information word consists of 4 periods as illustrated below. 1 / 3 b i t s y n c . p e r i o d p i l o t p e r i o d ( 1 2 b i t s ) a d d r e s s c o d e p e r i o d d a t a c o d e p e r i o d Composition of information Rev. 1.20 5 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
