- ADC 0809 is an 8 channel, 8 bit ADC. It can convert an analog voltage input into an 8 bit digital data output.
- To select an input out of 8 options, there are three select lines (C, B and A). We put a channel number on these lines (0…7) and latch it using ALE. SOC signal is given to indicate start of conversion.
- The channel voltage is internally sampled and held into a capacitor. Conversion takes place internally using “Successive Approximations Algorithm”.
- Reference voltage for conversion is provided using +Vref and –Vref. The clock supply needed for conversion is given through CLK (typically ~ 1MHz).
- The end of conversion is indicated by the ADC using EOC signal. Now we give the OE signal enabling 8-bit data output from the ADC to 8255.
- This data from 8255 is now transferred to the microprocessor. The process is repeated for subsequent channels, by changing the channel number. ADCs have a vast use in the modern electronic world for Data Acquisition Systems. They can be used for temperature sensing, voice recording, speed sensing etc.
- Interfacing of ADC 0809 with 8086 using 8255 is represented in figure below:
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