HT12E

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 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’

Pin Assignment:


Pin Description:
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:



Applications
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

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HT12D

General Description:
The 212 decoders are a series of CMOS LSIs for remote control system applications. They are paired with Holtek s212 series of encoders (refer to the encoder/de- coder cross reference table). For proper operation, a pair of encoder/decoder with the same number of ad- dresses and data format should be chosen.
The decoders receive serial addresses and data from a programmed 212 series of encoders that are transmitted by a carrier using an RF or an IR transmission medium. They compare the serial input data three times continu-
ously with their local addresses. If no error or un- matched codes are found, the input data codes are decoded and then transferred to the output pins. The VT pin also goes high to indicate a valid transmission. The 212 series of decoders are capable of decoding informations that consist of N bits of address and 12N bits of data. Of this series, the HT12D is arranged to pro- vide 8 address bits and 4 data bits, and HT12F is used to decode 12 bits of address information.
BLOCK DIAGRAM:

Functional Description:
Operation The 212 series of decoders provides various combina- tions of addresses and data pins in different packages so as to pair with the 212 series of encoders.
The decoders receive data that are transmitted by an encoder and interpret the first N bits of code period as addresses and the last 12N 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 12N 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.

Pin assignment:

A0~A7 : Input pins for address A0~A7 setting These pins can be externally set to VSS or left open.
D8~D11: Output data pins, power-on state is low.
DIN: Serial data input pin
VT: Valid transmission, active high
OSC1: Oscillator input pin
OSC2: Oscillator output pin
VSS: Negative power supply, ground
VDD: Positive power supply

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