From 162e5032918c4caab1a2d4875c4ae2b0598c02c2 Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Tue, 2 Jul 2019 15:54:07 -0400
Subject: [PATCH] sms/vdp: properly protect AF on PutC

---
 kernel/sms/vdp.asm | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/sms/vdp.asm b/kernel/sms/vdp.asm
index 8e59dba..deef471 100644
--- a/kernel/sms/vdp.asm
+++ b/kernel/sms/vdp.asm
@@ -133,6 +133,8 @@ vdpPutC:
 	cp	ASCII_BS
 	jr	z, vdpBS
 
+	push	af
+
 	; ... but first, let's convert it.
 	call	vdpConv
 
@@ -140,20 +142,21 @@ vdpPutC:
 	call	vdpSpitC
 
 	; Move cursor. The screen is 32x24
-	ex	af, af'
 	ld	a, (VDP_ROW)
 	cp	31
 	jr	z, .incline
 	; We just need to increase row
 	inc	a
 	ld	(VDP_ROW), a
-	ex	af, af'		; bring back orig A
+
+	pop	af
 	ret
 .incline:
 	; increase line and start anew
-	ex	af, af'		; bring back orig A
 	call	vdpCR
-	jr	vdpLF
+	call	vdpLF
+	pop	af
+	ret
 
 vdpCR:
 	call	vdpClrPos