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 12N data bits. Each ad- dress/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 ap- plication flexibility of the 212 series of encoders. The HT12A additionally provides a 38kHz car- rier for infrared systems.
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 en- coder output completes its final cycle and then stops as shown below.
Function Address No. Address/ Data No. Oscillator Trigger
8 4 RC oscillator TE’
A0~A7: Input pins for address A0~A7 setting These pins can be externally set to VSS or left open
AD8~AD11: Input pins for address/data AD8~AD11 setting These pins can be externally set to VSS or left open
DOUT: Encoder data serial transmission output
TE’: Transmission enable, active low
OSC1: Oscillator input pin
OSC2: Oscillator output pin
VSS : Negative power supply, grounds
VDD: Positive power supply
Absolute Maximum Ratings
Supply Voltage (HT12E) ...............0.3V to 13V
Input Voltage....................VSS0.3 to VDD+0.3V
Storage Temperature.................50C to 125 C
Operating Temperature...............20C to 75 C
Address/data programming (preset):
The status of each address/data pin can be individually pre-set to logic high or low. If a transmis- sion-enable signal is applied, the encoder scans and transmits the status of the 12 bits of ad- dress/data serially in the order A0 to AD11 for the HT12E encoder and A0 to D11 for the HT12A encoder.
During information transmission these bits are transmitted with a preceding synchronization bit. If the trigger signal is not applied, the chip enters the standby mode and consumes a reduced current of less than 1 A for a supply voltage of 5V. Usual applications preset the address pins with individual security codes using DIP switches or PCB wiring, while the data is selected by push buttons or electronic switches.
The following figure shows an application using the HT12E:
The transmitted information is as shown:
1. Burglar alarm system
2. Smoke and fire alarm system
3. Garage door controllers
4. Car door controllers
5. Car alarm system
6. Security system
7. Cordless telephones
8. Other remote control systems