The 212 decoders are a series of CMOS LSIs for remote control system applications. They are paired with Holtek¢s 212 series of encoders (re- fer to the encoder/decoder cross reference ta- ble). 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 se- rial input data three times continuously with their local addresses. If no error or unmatched codes are found, the input data codes are de- coded 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 decod- ing informations that consist of N bits of ad- dress and 12-N bits of data. Of this series, the HT12D is arranged to provide 8 address bits and 4 data bits, and HT12F is used to decode 12 bits of address information.