--8-bit Analogue to Digital Converter--8-bit analogue to digital converter--demonstrates use of LOOP and WAIT statementsENTITY adc8 ISGENERIC(tconv : TIME := 10 us); --conversion timePORT(vin : IN REAL RANGE 0.0 TO +5.0; --unipolar inputdigout : OUT NATURAL RANGE 0 TO 255; --outputsc : IN BIT; busy : OUT BIT); --controlEND adc8;ARCHITECTURE behaviour OF adc8 ISBEGINPROCESSVARIABLE digtemp : NATURAL;CONSTANT vlsb : REAL := 5.0/256; --least significant bit valueBEGINdigtemp := 0;WAIT UNTIL (sc'EVENT AND sc = '0'); --falling edge on sc starts convbusy <= '1'; --flag converter busyWAIT FOR tconv; --conversion timeFOR i IN 0 TO 255 LOOP --do ramp-up conversionIF vin >= REAL(i)*vlsbTHEN IF digtemp = 255 THEN EXIT;ELSE digtemp := digtemp + 1;END IF;ELSE EXIT;END IF;END LOOP;digout <= digtemp; --output resultbusy <= '0'; --flag end of conversionEND PROCESS;END behaviour;