* Subroutine that receives as input in A the address of the analog channel. 
* The subroutine starts the conversion of the specified channel, 
* waits for the end of conversion and returns the conversion result in A.

READ_ADC	ANDA	#$F8	;keep only the channel address
		STAA	ADCTL	;start conversion MULT=SCAN=0
POLL_ADC	LDAA	ADCTL	
		ANDA	#$80	;poll CCF until true
		BEQ	POLL_ADC	
		LDAA	ADR1	;get result in A
		RTS		;return 
