23-09-2013, 04:47 PM
Series of Decoders
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 further enhances the application flexibility of the 212 series of encoders
Features
Operating voltage: 2.4V~12V
Low power and high noise immunity CMOS technology
Low standby current
Capable of decoding 12 bits of information
Address/Data number combination
HT12D: 8 address bits and 4 data bits
Built-in oscillator needs only 5% resistor
Valid transmission indicator
Easy interface with an RF or an infrared transmission medium
Minimal external components
Operation:
The 212 series of decoders provides various combinations of addresses and data pins in different packages so as to pair with the 212series 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 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 address and data. The decoders will then check the received address three times continuously. If the received address codes all match the contents of the decode local address, the 12_N bits of data are decoded to activate 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 transmission is valid. Otherwise it is always low.