1. CS, Chip Select:
2. RD, Read: This is an input pin and active low. After converting the analog data, the ADC stores the result in an internal register. This pin is used to get the data out of the ADC 0804 chip. When CS=0 & high to low pulse is given to this pin, the digital output is shown on the pins D0-D7.
3. WR, Write: This is an input pin and active low. This is used to instruct the ADC to start the conversion process. If CS=0 and WR makes a low to high transition, the ADC starts the conversion process.
4. CLK IN, Clock IN: This is an input pin connected to an external clock source.
5. INTR, Interrupt: This is an active low output pin. This pin goes low when the conversion is over.
6. Vin+ : Analog Input .
7. Vin- : Analog Input. Connected to ground.
8. AGND: Analog Ground.
9. Vref/2: This pin is used to set the reference voltage. If this is not connected the default reference voltage is 5V. In some application it is required to reduce the step size. This can be done by using this pin.
10. DGND: Digital Ground.
11-18. Output Data Bits (D7-D0).
19. CLKR: Clock Reset.
20. Vcc: Positive Supply