From c6ed0f0d00ce76d38357a0f51b6a2334eea3620a Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Sat, 30 Jan 2021 17:07:11 +0100
Subject: [PATCH] added memory clearing, improved debug code

---
 src/zvm_m65/debug.s        |  2 +-
 src/zvm_m65/z80_dispatch.s |  2 +-
 src/zvm_m65/z80_reset.s    | 26 ++++++++++++++++++++++++--
 src/zvm_m65/zvm.s          |  4 ++--
 src/zvm_m65/zvm_bios.s     |  4 ++--
 5 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/src/zvm_m65/debug.s b/src/zvm_m65/debug.s
index 9f39401a..73d9618a 100644
--- a/src/zvm_m65/debug.s
+++ b/src/zvm_m65/debug.s
@@ -54,7 +54,7 @@ DBG_print_hex:
 	jsr CHROUT
 	pla
 	jsr DBGINT_print_hex_byte
-	jmp DBGINT_end
+	bra DBGINT_end
 
 
 
diff --git a/src/zvm_m65/z80_dispatch.s b/src/zvm_m65/z80_dispatch.s
index 9d0132fc..00dc7f18 100644
--- a/src/zvm_m65/z80_dispatch.s
+++ b/src/zvm_m65/z80_dispatch.s
@@ -9,7 +9,7 @@
 
 	+Z80_FETCH_VIA_PC_INC
 
-	; jsr DBG_print_PC_opcode
+	jsr DBG_print_PC_opcode
 
 	asl
 	tax
diff --git a/src/zvm_m65/z80_reset.s b/src/zvm_m65/z80_reset.s
index dd8ba8ea..bddecbe5 100644
--- a/src/zvm_m65/z80_reset.s
+++ b/src/zvm_m65/z80_reset.s
@@ -1,10 +1,10 @@
 
 ;
-; Z80 CPU reset
+; Z80 CPU/memory reset
 ;
 
 
-Z80_reset:
+Z80_reset_CPU:
 
 	; Reset registers and internal emulation data
 	
@@ -36,3 +36,25 @@ Z80_reset:
 	; Default bank is 1 (the one user software runs from)	
 
 	jmp ZVM_set_bank_1
+
+
+Z80_reset_MEM:
+
+	lda #$05
+	sta BIOS_LOADPTR+2
+	lda #$00
+	sta BIOS_LOADPTR+0
+	sta BIOS_LOADPTR+1
+	sta BIOS_LOADPTR+3
+
+@loop:
+
+	dec BIOS_LOADPTR+2
+	sta [BIOS_LOADPTR],z
+	inc BIOS_LOADPTR+2
+	sta [BIOS_LOADPTR],z
+
+	inw BIOS_LOADPTR
+	bne @loop
+
+	rts
diff --git a/src/zvm_m65/zvm.s b/src/zvm_m65/zvm.s
index e22212b7..8cdbf8c2 100644
--- a/src/zvm_m65/zvm.s
+++ b/src/zvm_m65/zvm.s
@@ -56,8 +56,8 @@ ZVM: ; entry point
 	; Generate CPU tables, reset the CPU
 
 	jsr Z80_table_gen
-	jsr Z80_reset
-	; XXX Z80 clear memory here
+	; XXX jsr Z80_reset_MEM
+	jsr Z80_reset_CPU
 
 	; Try CPU test
 
diff --git a/src/zvm_m65/zvm_bios.s b/src/zvm_m65/zvm_bios.s
index 86d6b7f4..e3454ff0 100644
--- a/src/zvm_m65/zvm_bios.s
+++ b/src/zvm_m65/zvm_bios.s
@@ -55,9 +55,9 @@ zvm_BIOS_00_BOOT:            ; Cold start
 
 	; XXX fetch RAM disk image, CPM3.SYS, command interpreter
 	; XXX close all the files, reset I/O, set screen mode
-	; XXX clear memory
 
-	jsr Z80_reset
+	jsr Z80_reset_MEM
+	jsr Z80_reset_CPU
 
 	; FALLTROUGH