ca65 V2.17 - Git 582aa41
Main file   : hex_to_decimal.ca65
Current file: hex_to_decimal.ca65

000000r 1               ;
000000r 1               ; ACORN System 1 Applications: Hexadecimal To Decimal
000000r 1               ;
000000r 1               ; From the Acorn System 1 User's Manual
000000r 1               ;
000000r 1               ; (Chris Oddy January 2022)
000000r 1               ;
000000r 1               ; entry point $0200
000000r 1               ;
000000r 1               		.setcpu			"6502"
000000r 1               		.listbytes		unlimited
000000r 1               ;
000000r 1               HEXL	:=		$20
000000r 1               HEXH	:=		$21
000000r 1               DECOUT	:=		$22
000000r 1               QHEXTD1	:=		$FE64		; quad hex to display 1
000000r 1               HEXTD	:=		$FE7A		; hex to display
000000r 1               QDATFET	:=		$FE88		; quad data fetch
000000r 1               RESTART	:=		$FF04		; Monitor reentry point
000000r 1               ;
000000r 1               		.org			$0200
000200  1               ;
000200  1  84 20        HEXDEC:	sty		HEXL		; set up zero prompt
000202  1  84 21        		sty		HEXH
000204  1  A2 20        		ldx		#HEXL
000206  1  20 88 FE     		jsr		QDATFET		; and fetch the data
000209  1  F8           		sed					; decimal mode
00020A  1  A2 00        		ldx		#$00		; set X & Y & DECOUT to zero
00020C  1  86 22        		stx		DECOUT
00020E  1  A5 20        DECRHX:	lda		HEXL		; test for zero, then decrement
000210  1  D0 06        		bne		NODEC
000212  1  A5 21        		lda		HEXH
000214  1  F0 13        		beq		DEAD		; if hex No. zero, then finished
000216  1  C6 21        		dec		HEXH
000218  1  C6 20        NODEC:	dec		HEXL
00021A  1  18           		clc					; add 1 to decimal number,
00021B  1  98           		tya					; using X & Y as two byte accumulator
00021C  1  69 01        		adc		#$01
00021E  1  A8           		tay
00021F  1  8A           		txa
000220  1  69 00        		adc		#$00
000222  1  AA           		tax
000223  1  90 E9        		bcc		DECRHX
000225  1  E6 22        		inc		DECOUT
000227  1  B0 E5        		bcs		DECRHX
000229  1  84 20        DEAD:	sty		HEXL		; finished, so store X & Y
00022B  1  86 21        		stx		HEXH
00022D  1  A2 20        		ldx		#HEXL
00022F  1  20 64 FE     		jsr		QHEXTD1		; display 4 digits
000232  1  88           		dey
000233  1  A5 22        		lda		DECOUT
000235  1  20 7A FE     		jsr		HEXTD		; display 5th digit
000238  1  4C 04 FF     		jmp		RESTART
000238  1