multiply by 40 routine

git-svn-id: svn://svn.cc65.org/cc65/trunk@118 b7a2c559-68d2-44c3-8de9-860c34a00d81
2024-12-22 12:30:41 +00:00 · 2000-06-23 22:06:37 +00:00 · 2000-06-23 22:06:37 +00:00 · e51b5c8b59
commit e51b5c8b59
parent 7b944cae11
1 changed files with 35 additions and 0 deletions
--- a/libsrc/atari/mul40.s
+++ b/libsrc/atari/mul40.s
@ -0,0 +1,35 @@
+;
+; Christian Groessler, June 2000
+;
+; mul40
+; multiplies A by 40 and returns result in AX
+; uses tmp4
+
+	.importzp	tmp4
+	.export		mul40
+
+.proc	mul40
+
+	ldx	#0
+	stx	tmp4
+	sta	loc_tmp
+	asl	a
+	rol	tmp4
+	asl	a
+	rol	tmp4		; val * 4
+	adc	loc_tmp
+	bcc	L1
+	inc	tmp4		; val * 5
+L1:	asl	a
+	rol	tmp4		; val * 10
+	asl	a
+	rol	tmp4
+	asl	a
+	rol	tmp4		; val * 40
+	ldx	tmp4
+	rts
+
+.endproc
+
+	.bss
+loc_tmp:.res	1