From 8c880c339000010260a927c3a0f28f9049b8a0b8 Mon Sep 17 00:00:00 2001
From: mrb0nk500 <b0nk@b0nk.xyz>
Date: Mon, 5 Oct 2020 11:15:21 -0400
Subject: - Fixed the rotate instructions.

  The carry flag is now set properly, and the rotation
  now is set properly by the carry flag, even for
  shift values greater than one.

- Added a test program for properly testing the rotate
  instructions.
---
 test/rotate.s | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 test/rotate.s

(limited to 'test')

diff --git a/test/rotate.s b/test/rotate.s
new file mode 100644
index 0000000..6115e94
--- /dev/null
+++ b/test/rotate.s
@@ -0,0 +1,61 @@
+; Test rol, and ror.
+
+.org 0
+count:
+	.res 1
+tmp:
+	.res 8
+
+.org $8000
+reset:
+	cps		;
+	ldx.w #$FFFF	;
+	txs		;
+	and #0		;
+	tax		;
+	tab		;
+	tay		;
+
+
+start:
+	ldb #8		; Set the loop count to 8.
+@loop:
+	lda #$AA	; Set A to magic byte.
+	deb		; Decrement the loop count.
+	beq @savemagic	; Save the magic number, if the loop count is zero.
+	lsl #8		; Shift the magic number by one byte, if the loop count is non zero.
+	bra @loop	; Keep looping.
+@savemagic:
+	sta.q tmp	; Save the magic number.
+
+
+rotate:
+	ldb #0		; Reset B.
+@loop:
+	and #0		; Reset A.
+	lda #$40	; Set the shift count to 64.
+	sta count	;
+	lda.q tmp	; Get our magic number.
+	inb		; Increment our shift amount by one.
+	cpb #$40	; Is the shift amount greater than, or equal to 64?
+	bcs rotate	; Yes, so reset B.
+@rotl:
+	rol b		; Rotate the magic number left by our shift amount.
+	dec count	; Decrement the shift count.
+	beq @rotr	; Start rotating right, if the shift count is zero.
+	bra @rotl	; Keep looping, if the shift count is non zero.
+@rotr:
+	and #0		; Reset A.
+	lda #$40	; Set the shift count to 64.
+	sta count	;
+	lda.q tmp	; Get our magic number.
+@rotr2:
+	ror b		; Rotate the magic number right by our shift amount.
+	dec count	; Decrement the shift count.
+	beq @loop	; Increment the shift amount, if the shift count is zero.
+	bra @rotr2	; Keep looping, if the shift count is non zero.
+
+.org $FFC0
+.qword reset
+a
+d
-- 
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