; EXPERIMENTAL 
; 2 DIGIT 7 SEGMENT LED DRIVER (COMMON CATHODE)

ifdef __SASM
  DEVICE SX28L, OSCHS3, STACKX, OPTIONX
  IRC_CAL IRC_FAST
  FREQ 50_000_000
else
  DEVICE SX28AC, OSCHS, OPTIONX
endif
DEVICE TURBO
RESET Start


org	$08
value	ds 1
columns	ds 1
counter ds 1
digit	ds 1
digits	ds 2


;-------------------------------------------------------------------
;	SUBROUTINE TO CLEAR MEMORY REGISTERS
;-------------------------------------------------------------------
ClearData
  sb	fsr.4
    Setb fsr.3
  clr	ind
  ijnz	fsr, ClearData
  ret

;-------------------------------------------------------------------
;	SUBROUTINE RETURNS 7-SEGMENT CODING IN W
;	WHEN CALLED WITH A HEXIDECIMAL DIGIT IN W
;
;	NOTE: POSITIVE LOGIC - 1-BITS TURN ON THE ASSOCIATED LED
;-------------------------------------------------------------------

Decode
  jmp	pc+w

;  SEGMENTS
;
;	DCGBE.FA
   retw	%11011011	;0
   retw	%01010000	;1
   retw	%10111001	;2
   retw	%11110001	;3
   retw	%01110010	;4
   retw	%11100011	;5
   retw	%11101011	;6
   retw	%01010001	;7
   retw	%11111011	;8
   retw	%11110011	;9
   retw	%01111011	;A
   retw	%11101010	;b
   retw	%10001011	;C
   retw	%11111000	;d
   retw	%10101011	;E
   retw	%00101011	;F


;------------------------------------------------
;	MAIN PROGRAM
;------------------------------------------------
org	$100
Start
  clr 	fsr
  call 	ClearData

  mov 	!ra, #%1100		; Outputs for Cathodes (Columns)
  mov 	!rc, #%00000000	; Outputs for Anodes (Segments)

Loop 
  mov		digits, #$8
  mov		digits+1, #$A
  mov 	counter, #3		; Number of 7-Seg Displays (+ 1)
  mov 	columns, #%0001	; 1st Column

  mov		w, digits		; SET 1st DIGIT
  call 	Decode		; 
  mov 	digit, w		; 
 
:Loop
  dec		counter
  snz
    jmp	Loop		; JUMP TO OUTER LOOP 
  mov 	ra, columns
  mov 	rc, digit
  rl		columns	; Next Column

  mov		w, digits+1	; SET 2nd DIGIT
  call 	Decode	; 
  mov 	digit, w	; 
  
  jmp 	:Loop		; JUMP TO INNER LOOP

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