From 5d7a24241cee19434f1ac8352c7f74eac7b410de Mon Sep 17 00:00:00 2001
From: =?utf8?q?Stephan=20M=C3=BChlstrasser?= <stephan.muehlstrasser@web.de>
Date: Sat, 8 Nov 2014 01:14:46 +0100
Subject: [PATCH] Implemented clrscr routine for C1P

---
 libsrc/c1p/c1p.inc  |  3 +++
 libsrc/c1p/clrscr.s | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+)
 create mode 100644 libsrc/c1p/c1p.inc
 create mode 100644 libsrc/c1p/clrscr.s

diff --git a/libsrc/c1p/c1p.inc b/libsrc/c1p/c1p.inc
new file mode 100644
index 000000000..525a8e9ee
--- /dev/null
+++ b/libsrc/c1p/c1p.inc
@@ -0,0 +1,3 @@
+
+SCRNBASE       := $D000        ; Base of video RAM
+VIDEORAMSIZE   := $0400        ; Size of C1P video RAM (1 kB)
diff --git a/libsrc/c1p/clrscr.s b/libsrc/c1p/clrscr.s
new file mode 100644
index 000000000..f219a4550
--- /dev/null
+++ b/libsrc/c1p/clrscr.s
@@ -0,0 +1,23 @@
+;
+; void clrscr (void);
+;
+        .export         _clrscr
+        .include        "c1p.inc"
+
+; Adapted from the Challenger Character Graphics
+; Reference Manual, "2.3.3 MACHINE LANGUAGE SCREEN CLEAR"
+; This is self-modifying code!
+BANKS = VIDEORAMSIZE / $100
+
+_clrscr:	LDA #$20 ;' '
+		LDY #BANKS
+		LDX #$00
+STALOC:		STA SCRNBASE,X
+		INX
+		BNE STALOC
+		INC STALOC+2
+		DEY
+		BNE STALOC
+		LDA #>(SCRNBASE) ; load high byte
+		STA STALOC+2     ; restore base address
+		RTS
-- 
2.39.5