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Tuesday, September 6, 2011

HT12D DECODER for Engineering projects

HT12D DECODER  for Engineering projects

The 212 decoders are a series of CMOS LSIs for remote control system applications. They are paired with Holtek 212 series of encoders (refer to the encoder/decoder cross reference table). For proper operation, a pair of encoder/decoder with the same number of addresses 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 continuously with their local addresses. If no error or unmatched 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 information that consists of N bits of address and 12_N bits of data. Of this series, the HT12D is arranged to provide 8 address bits and 4 data bits. Operation The 212 series of decoders provides various combinations 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 12_N bits as data, where N is the address code number.

The oscillator is disabled in the standby state and activated when a logic high signal applies to the DIN pin. That is to say, the DIN should be kept low if there is no signal input. The received data and address is checked thrice before setting the VT high.

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