Explain the pin diagram of ADC 0808/0809 and method of interfacing to 8086 microprocessor with a suitable example.

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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:

Interfacing of ADC 0809 and 8086 using 8255

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