INCLUDE 89C51.MC

;----------------------------------------------------------
; Microcontroller connections to ADC0808/9 lines.
CONTROL	EQU	P3		; All control signals
ADD_A		EQU	P3.0		; Pin 25 ADD A
ADD_B		EQU	P3.1		; Pin 24 ADD B
ADD_C		EQU	P3.2		; Pin 23 ADD C

START		EQU	P3.3		; Pin 6 Start
EOC		EQU	P3.4		; Pin 7 EOC
OE		EQU	P3.5		; Pin 9 Output Enable
ALE		EQU	P3.6 		; Pin 22 ALE

DATA		EQU	P1		; Data Lines
;----------------------------------------------------------
; Register definitions.

ADDRESS	EQU	00h		; Address pointer
BUFFER	EQU	01h		; Data register
;----------------------------------------------------------
on_reset:
;Initialize ADC

	MOV CONTROL,#00H		; Make all control signals low
	MOV DATA,#FFH		; Data lines for input
	
	MOV ADDRESS,#02H		; Analog channel address
	CALL read_adc		; Get Adc data for given channel in A
	MOV A,BUFFER		; Data in acc
	
ENDLESS:
	JMP ENDLESS	
;----------------------------------------------------------	
read_adc:
	; Read one byte of data from adc.
	; Performs a analog conversion cycle.
	; address of channel in register "ADDRESS",
	; Returns data in BUFFER
	; Destroys A.
		CLR OE		; Disable output
		
		MOV A,ADDRESS
		ANL A,#07H
		ANL CONTROL,#F8H
		ORL CONTROL,A	; Send address of analog channel
		
		SETB ALE		; Latch the address
		NOP
		NOP
		SETB START		; Start the conversion
		NOP
		CLR ALE
		NOP
		NOP
		CLR START
		NOP
		NOP
		
EOCLOOP:	
		JNB EOC, EOCLOOP	; Do until EOC high

		SETB OE		; Output Enable
		MOV BUFFER,DATA	; Get data in buffer
		
		RET		
;---------------------------------------------------------