As shown in the typical circuit, ADC0804 can be interfaced with any microcontroller. You need a minimum of 11 pins to interface ADC0804, eight for data pins and 3 for control pins. As shown in the typical circuit the chip select pin can be made low if you are not using the microcontroller port for any other peripheral (multiplexing).

There is a universal rule to find out how to use an IC. All you need is the datasheet of the IC you are working with and take a look at the timing diagram of the IC which shows how to send the data, which signal to assert and at what time the signal should be made high or low etc.

Note: Keep this in mind that whenever you are working with an IC and you want to know how to communicate with that IC, then simply look into the timing diagram of that IC from its datasheet. It gives you complete information that you need regarding the communication of IC.

Start Conversion Timing Diagram

End of Conversion Timing Diagram

The above timing diagrams are from ADC0804 datasheet. The first diagram (FIGURE 10A) shows how to start a conversion. Also you can see which signals are to be asserted and at what time to start a conversion. So looking into the timing diagram FIGURE 10A. We note down the steps or say the order in which signals are to be asserted to start a conversion of ADC. As we have decided to make Chip select pin as low so we need not to bother about the CS signal in the timing diagram. Below steps are for starting an ADC conversion. I am also including CS signal to give you a clear picture. While programming we will not use this signal.

1. Make chip select (CS) signal low.
2. Make write (WR) signal low.
3. Make chip select (CS) high.
4. Wait for INTR pin to go low (means conversion ends).

Once the conversion in ADC is done, the data is available in the output latch of the ADC. Looking at the FIGURE 10B which shows the timing diagram of how to read the converted value from the output latch of the ADC. Data of the new conversion is only avalable for reading after ADC0804 made INTR pin low or say when the conversion is over. Below are the stepts to read output from the ADC0804.

1. Make chip select (CS) pin low.
2. Make read (RD) signal low.
4. Make read (RD) signal high.
5. Make chip select (CS) high.

```.include "8515def.inc"

.equ rd = PORTB0           ;Read signal PortB.0
.equ wr = PORTB1           ;Write Signal PortB.1
.equ cs = PORTB2           ;Chip Select PortB.2
.equ intr = PORTB3         ;INTR signal PortB.3
.def temp = r17            ;Temporary register

.org 0x00
start:
out SPL,temp           ;RAMEND - highest value
ldi temp,high(RAMEND)  ;of internal SRAM
out SPH,temp

sbi DDRB,rd            ;Make RD as o/p
sbi DDRB,wr            ;Make WR as o/p
sbi DDRB,cs            ;Make CS as o/p
again:
ldi temp,0xFF
out DDRC,temp          ;Make PORTC as o/p Port
rjmp again             ;Do it again

conv:                      ;Start conversion
cbi PORTB,cs           ;Make CS low
cbi PORTB,wr           ;Make WR low
nop
sbi PORTB,wr           ;Make WR high
sbi PORTB,cs           ;Make CS high
wait:
sbic PINB,intr         ;Wait for INTR signal
rjmp wait

ret                    ;Conversion done

cbi PORTB,cs           ;Make CS low
cbi PORTB,rd           ;Make RD low

sbi PORTB,rd           ;Make RD high
sbi PORTB,cs           ;Make CS high
```

```#include <avr/io.h>
#define rd PB0                           //Read signal PORTB0
#define wr PB1                           //Write signal PORTB1
#define cs PB2                           //Chip Select PORTB2
#define intr PB3                         //INTR signal PORTB3

void conv();                             //Start Conversion

int main(){
DDRB = (1<<rd)|(1<<wr)|(1<<cs);      //RD, WR, CS as output
DDRC = 0xFF;                         //PORTC as output
PORTC = 0xFF;
while(1){                            //Forever loop
conv();                          //Start of conversion
PORTC = adc_val;                 //Move it to PORTC
}
return 0;
}

void conv(){
PORTB = PORTB & (~((1<<cs)|(1<<wr))); //Make CS and WR low
PORTB = PORTB | ((1<<cs)|(1<<wr));    //Make CS and WR high
while(PINB&(1<<intr));                //Wait for INTR signal
}