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| The HT12E encodes 12 bits of information and then serially transmits it upon receipt of a transmit enable signal to its active low TE pin. The data is transmitted on the pin marked DOUT, and can be easily interfaced to work with RF or infra-red transmission networks. Complementing the encoder are two decoder ICs, the HT12F and HT12D. The HT12F takes the encoded signal and decodes the whole of the 12 bits as being address data. If the received address matches with the address preset on the decoder IC, then the decoder IC will make its valid transmission pin go high (VT). Using the HT12D device is very similar, with the single exception that it decodes the first 8 bits of information and checks them against the first 8 bits of address preset on its pins. When both addresses match, it makes available the last 4 bits of the received data word, on its four output pins. At the same time the decoder IC will send high its VT pin. This means that data can be sent from the encoder IC and only be decoded and therefore received by those decoder ICs with a matching 8bit address. Features of the devices are low power, high noise immunity, low stand-by current of 1╡A, wide operating voltage, 212 address code (28 for the HT12D), built-in oscillator requiring only a 5% resistor, four times transmission with three times receive check, and a minimum of external components. Applications include burglar alarm systems, smoke and fire alarm systems, car door controllers, car alarm systems, security systems, cordless telephones, and many remote control systems. |
| Operating voltage, VDD: |
2· 4V to 12V, 5V typ |
| (sink), IO: |
1· 6mA typ, 1mA min |
| (source): |
5mA typ, 2mA min |
| Stand-by current, ISTB: |
0· 1╡A typ, 1╡A max |
| HT12E, (FOSC=3kHz): |
40╡A typ, 80╡A max |
| (FOSC=200kHz): |
200╡A typ, 400╡A max |
| Recommended oscillator parameters: |
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1· 1M (3kHz) |
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750k (4· 3kHz) |
| NB. Recommend Fosc(HT12D & HT12F)≈Fosc(HT12E)*50 |
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