23-09-2013, 04:44 PM
212 Series of Encoders
General Description:
The 212 encoders are a series of CMOS LSIs for remote control system applications. They are capable of encoding information which consists of N address bits and 12_N data bits. Each address/data input can be set to one of the two logic states. The programmed addresses/data are transmitted together with the header bits via an RF or an infrared transmission medium upon receipt of a trigger signal. The capability to select a TE trigger on the HT12E or a DATA trigger on the HT12A further enhances the application flexibility of the 212 series of encoders. The HT12A additionally provides a 38 kHz carrier for infrared systems.
Features
Operating voltage
2.4V~5V for the HT12A
2.4V~12V for the HT12E
Low power and high noise immunity CMOS technology
Low standby current: 0.1_A (typ.) at
VDD = 5V
Minimum transmission word
Four words for the HT12E
Built-in oscillator needs only 5% resistor
Data code has positive polarity
Minimal external components
Operation
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.