From aeccd3a776fd94f2d43d4e2b4c8eb140124ceed7 Mon Sep 17 00:00:00 2001
From: "ol.sc" <ol.sc@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Fri, 11 Sep 2009 16:27:20 +0000
Subject: [PATCH] Allow to run programs as ProDOS SYS files (beside BIN files).
 To do so detect at runtime if BASIC.SYSTEM is present by checking the
 "signature" of the last system bitmap byte.

git-svn-id: svn://svn.cc65.org/cc65/trunk@4146 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 libsrc/apple2/crt0.s | 76 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 59 insertions(+), 17 deletions(-)

diff --git a/libsrc/apple2/crt0.s b/libsrc/apple2/crt0.s
index 4985a87bf..9ba7f9534 100644
--- a/libsrc/apple2/crt0.s
+++ b/libsrc/apple2/crt0.s
@@ -99,14 +99,14 @@ _exit:  ldx     #<exit
         jsr     donelib
 
         ; Check for valid interrupt vector table entry number
-        lda     intnum
+        lda     int_num
         beq     exit
 
         ; Deallocate interrupt vector table entry
-        dec     params		; Adjust parameter count
+        dec     i_param		; Adjust parameter count
         jsr     $BF00		; MLI call entry point
         .byte   $41		; Dealloc interrupt
-        .addr   params
+        .addr   i_param
 
         ; Restore the original RESET vector
 exit:   ldx     #$02
@@ -128,8 +128,8 @@ exit:   ldx     #$02
         ldx     #$FF
         txs                     ; Re-init stack pointer
 
-        ; Back to DOS
-        jmp     DOSWARM
+        ; We're done
+        jmp     (done)
 
 ; ------------------------------------------------------------------------
 
@@ -159,25 +159,47 @@ init:   ldx     #zpspace-1
         lda     #>_exit
         jsr     reset		; Setup RESET vector
 
-        ; Setup the stack
-        lda     HIMEM
-        sta     sp
-        lda     HIMEM+1
-        sta     sp+1   	    	; Set argument stack ptr
+        ; Check for ProDOS
+        ldy     $BF00		; MLI call entry point
+        cpy     #$4C		; Is MLI present? (JMP opcode)
+        bne     basic
+        
+        ; Check ProDOS system bit map
+        lda     $BF6F           ; protection for pages $B8 - $BF
+        cmp     #%00000001      ; exactly page $BF is protected
+        bne     basic
+
+        ; No BASIC.SYSTEM so quit to ProDOS dispatcher instead
+        lda     #<quit
+        ldx     #>quit
+        sta     done
+        stx     done+1
+        
+        ; No BASIC.SYSTEM so use addr of ProDOS system global page
+        lda     #<$BF00
+        ldx     #>$BF00
+        bne     :+              ; Branch always
+
+        ; Get highest available mem addr from BASIC interpreter
+basic:  lda     HIMEM
+        ldx     HIMEM+1
+
+        ; Setup the C stack
+:       sta     sp
+        stx     sp+1
 
         ; Check for interruptors
         lda     #<__INTERRUPTOR_COUNT__
         beq     :+
 
         ; Check for ProDOS
-        lda     $BF00		; MLI call entry point
-        cmp     #$4C		; Is MLI present? (JMP opcode)
+        cpy     #$4C		; Is MLI present? (JMP opcode)
         bne     prterr
 
         ; Allocate interrupt vector table entry
         jsr     $BF00		; MLI call entry point
         .byte   $40		; Alloc interrupt
-        .addr   params
+        .addr   i_param
         bcs     prterr
 
 	; Enable interrupts as old ProDOS versions (i.e. 1.1.1)
@@ -223,7 +245,7 @@ msglen = * - errmsg
 
         ; ProDOS TechRefMan, chapter 6.2:
         ; "Each installed routine must begin with a CLD instruction."
-intrpt: cld
+intptr: cld
 
         ; Call interruptors and check for success
         jsr     callirq
@@ -248,13 +270,33 @@ reset:  stx     SOFTEV
         sta     PWREDUP
         rts
 
+        ; Quit to ProDOS dispatcher
+quit:   jsr     $BF00           ; MLI call entry point
+        .byte   $65             ; Quit
+        .word   q_param
+
+; ------------------------------------------------------------------------
+
+        .rodata
+
+        ; MLI parameter list for quit        
+q_param:.byte   $04		; param_count
+        .byte   $00		; quit_type
+        .word   $0000		; reserved
+        .byte   $00		; reserved
+        .word   $0000		; reserved
+	
 ; ------------------------------------------------------------------------
 
         .data
 
-params: .byte   $02		; Parameter count
-intnum: .byte   $00		; Interrupt number
-        .addr   intrpt		; Interrupt handler
+        ; MLI parameter list for (de)alloc interrupt
+i_param:.byte   $02		; param_count
+int_num:.byte   $00		; int_num
+        .addr   intptr		; int_code
+
+        ; Location to jump to when we're done
+done:   .addr   DOSWARM
 
 ; ------------------------------------------------------------------------
 
-- 
2.39.5