;; A useful function to display a byte as a 3-digit decimal number .txt_output equ &bb5a ;;------------------------------------------- ;; DISPLAY A BYTE AS A 3-DIGIT DECIMAL NUMBER ;; ;; Enter: ;; A = 8-bit value ;; ;; Exit: ;; AF,BC corrupt. All other registers preserved ;; ;; NOTE: A) The display routine works by the following procedure: ;; ;; 1) The 8-bit value is divided by 100 then 10 and finally 1 to obtain ;; each digit value. Therefore 983 would produce 9,8 and 3 as each ;; digit. ;; 2) The digit is converted into ASCII form, and displayed. ;; 3) The remainder of the division, is used for the next division. ;; i.e. 983 divided by 100, leaves 83 as the remainder. This is ;; divided by 10, to give 3 as the remainder. ;; ;; B) In the routine, ;; ;; B = divisor (100,10,1) ;; C = digit value ;; A = dividend (8-bit value) ;; .print_decimal_byte ld b,100 ;divisor to obtain 100's digit value call print_decimal_digit ;display digit ld b,10 ;divisor to obtain 10's digit value call print_decimal_digit ;display digit ld b,1 ;divisor to obtain 1's digit value ;;------------------------------------------------ ;; B = divisor ;; A = dividend .print_decimal_digit ;;----------------------------------------------- ;; simple division routine ld c,0 ;zeroise result .decimal_divide sub b ;subtract divisor jr c,display_decimal_digit ;if dividend is less than divisor, the division ;has finished. inc c ;increment digit value jr decimal_divide .display_decimal_digit add a,b ;add divisor because dividend was negative, ;leaving remainder. ;;-------------------------------------- ;; A = dividend ;; C = result of division ;;-------------------------------------- ;; digit is a number between 0..9 ;; convert this into a ASCII character '0'..'9' then display this push af ld a,c ;get digit value add a,"0" ;convert value into ASCII character call txt_output ;display digit pop af ret