From 5e8d2205e8da7f278087bf4c73fb9c1add969d29 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Fri, 29 Jan 2021 20:27:39 +0100
Subject: [PATCH] crude implementation of CP/M rutine $09

---
 src/zvm_m65/z80_instr_general.s | 18 +++++++++---------
 src/zvm_m65/zvm_cpmemu.s        | 29 +++++++++++++++++++++++++++++
 src/zvm_m65/zvm_cputest.s       |  8 ++++++--
 3 files changed, 44 insertions(+), 11 deletions(-)
 create mode 100644 src/zvm_m65/zvm_cpmemu.s

diff --git a/src/zvm_m65/z80_instr_general.s b/src/zvm_m65/z80_instr_general.s
index 414adb76..4ab50531 100644
--- a/src/zvm_m65/z80_instr_general.s
+++ b/src/zvm_m65/z80_instr_general.s
@@ -96,17 +96,17 @@ Z80_instr_37:                                                                  ;
 
 Z80_instr_76:                                                                  ; HALT
 
-	; Used to call BIOS routines
-	; XXX probably not the besta idea, GENCPC seems to do some relocations
+	; Used to call BIOS and simulated CP/M routines
 
-	ldx #$01 ; default BIOS function, warm start
+	+Z80_FETCH_VIA_PC_INC
+
+	cmp  #$FF                ; $FF = CP/M call
+	+beq zvm_CPMemu
+
+	inc $D021
+
+	ldx #$01                 ; default routine, warm boot
 
-	lda REG_PC+1
-	cmp #$FE ;
-	bne @1
-	lda REG_PC+0
-	sec
-	sbc #$64
 	cmp #33
 	bcs @1
 	tax
diff --git a/src/zvm_m65/zvm_cpmemu.s b/src/zvm_m65/zvm_cpmemu.s
new file mode 100644
index 00000000..2c58c979
--- /dev/null
+++ b/src/zvm_m65/zvm_cpmemu.s
@@ -0,0 +1,29 @@
+
+;
+; Z80 Virtual Machine CP/M simulation (just to run selected binaries)
+;
+
+
+zvm_CPMemu:
+
+	ldx REG_C
+	cpx #$09
+	beq zvm_CPMemu_09
+
+	; XXX implement additional functions if needed
+
+	; FALLTROUGH
+
+zvm_CPMemu_end:
+
+	jmp Z80_instr_C9         ; RET
+
+zvm_CPMemu_09:               ; C_WRITESTR
+
+	+Z80_FETCH_VIA_DE
+	cmp #'$'
+	beq zvm_CPMemu_end
+
+	jsr CHROUT
+	inw REG_DE
+	bra zvm_CPMemu_09
diff --git a/src/zvm_m65/zvm_cputest.s b/src/zvm_m65/zvm_cputest.s
index 3aae1781..11801c5f 100644
--- a/src/zvm_m65/zvm_cputest.s
+++ b/src/zvm_m65/zvm_cputest.s
@@ -105,8 +105,6 @@ ZVM_cputest:
 
 @loop3:
 
-	inc $D020
-
 	dew BIOS_LOADCOUNT
 	bmi @loop2
 
@@ -120,6 +118,12 @@ ZVM_cputest:
 
 @load_done:
 
+	; Close the file
+
+	lda #$20
+	sta HTRAP00
+	+nop
+
 	jsr PRIMM
 	!pet "      done", $0D, $0D, 0