From 96e87c49ee364e7dd591ae0fb357929ea8f25516 Mon Sep 17 00:00:00 2001
From: cuz <cuz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Fri, 22 Nov 2002 23:41:20 +0000
Subject: [PATCH] Fixed the break stuff

git-svn-id: svn://svn.cc65.org/cc65/trunk@1593 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 libsrc/plus4/break.s   | 43 +++++++-------------
 libsrc/plus4/crt0.s    | 90 +++++++++++++++++++++++++++++++++++++-----
 libsrc/plus4/plus4.inc |  4 +-
 3 files changed, 96 insertions(+), 41 deletions(-)

diff --git a/libsrc/plus4/break.s b/libsrc/plus4/break.s
index c51cc4b07..52c77127c 100644
--- a/libsrc/plus4/break.s
+++ b/libsrc/plus4/break.s
@@ -6,8 +6,8 @@
 ;
 
        	.export	   	_set_brk, _reset_brk
-	.destructor	_reset_brk
 	.export	       	_brk_a, _brk_x, _brk_y, _brk_sr, _brk_pc
+        .import         brk_jmp
 
 	.include      	"plus4.inc"
 
@@ -19,11 +19,11 @@ _brk_y:		.res   	1
 _brk_sr:	.res	1
 _brk_pc:	.res	2
 
-oldvec:       	.res	2   		; Old vector
+oldvec:       	.res	2      	   	; Old vector
 
 
 .data
-uservec:    	jmp	$FFFF		; Patched at runtime
+uservec:    	jmp	$FFFF  	   	; Patched at runtime
 
 
 .code
@@ -32,21 +32,12 @@ uservec:    	jmp	$FFFF		; Patched at runtime
 .proc	_set_brk
 
 	sta	uservec+1
-  	stx	uservec+2 	; Set the user vector
+  	stx	uservec+2      	; Set the user vector
 
-	lda	oldvec
-	ora	oldvec+1	; Did we save the vector already?
-       	bne	L1		; Jump if we installed the handler already
-
-	lda	BRKVec
- 	sta    	oldvec
- 	lda 	BRKVec+1
- 	sta	oldvec+1	; Save the old vector
-
-L1:	lda	#<brk_handler	; Set the break vector to our routine
-	ldx	#>brk_handler
-	sta	BRKVec
-	stx	BRKVec+1
+        lda	#<brk_handler  	; Set the break vector to our routine
+	sta	brk_jmp+1
+       	lda	#>brk_handler
+	sta	brk_jmp+2
 	rts
 
 .endproc
@@ -55,26 +46,20 @@ L1:	lda	#<brk_handler	; Set the break vector to our routine
 ; Reset the break vector
 .proc	_reset_brk
 
-	lda  	oldvec
-	ldx  	oldvec+1
-	beq  	@L9		; Jump if vector not installed
-	sta    	BRKVec
-	stx  	BRKVec+1
-	lda	#$00
-	sta	oldvec		; Clear the old vector
-	stx	oldvec+1
-@L9:	rts
+        lda     #$00
+        sta     brk_jmp+1
+        sta     brk_jmp+2       ; Reset the vector
+        rts
 
 .endproc
 
 
 
-; Break handler, called if a break occurs
+; Break handler, called if a break occurs. Note: Y is not on the stack!
 
 .proc	brk_handler
 
-	pla
-	sta	_brk_y
+       	sty	_brk_y
 	pla
 	sta	_brk_x
 	pla
diff --git a/libsrc/plus4/crt0.s b/libsrc/plus4/crt0.s
index 503d086d5..a2e33413d 100644
--- a/libsrc/plus4/crt0.s
+++ b/libsrc/plus4/crt0.s
@@ -5,7 +5,9 @@
 ;
 
 	.export		_exit
-	.import		initlib, donelib
+        .export         brk_jmp
+
+	.import		condes, initlib, donelib
 	.import	     	push0, _main, zerobss
 	.import	       	__IRQFUNC_TABLE__, __IRQFUNC_COUNT__
 
@@ -13,6 +15,11 @@
 	.include	"plus4.inc"
 
 
+; ------------------------------------------------------------------------
+; Constants
+
+IRQInd 	       	= $500	; JMP $0000 - used as indirect IRQ vector
+
 ; ------------------------------------------------------------------------
 ; Place the startup code in a special segment to cope with the quirks of
 ; plus/4 banking.
@@ -77,17 +84,44 @@ L1:	lda	sp,x
 
 	jsr	initlib
 
+; If we have IRQ functions, chain our stub into the IRQ vector
+
+        lda     #<__IRQFUNC_COUNT__
+      	beq	NoIRQ1
+      	lda	IRQVec
+       	ldx	IRQVec+1
+      	sta	IRQInd+1
+      	stx	IRQInd+2
+      	lda	#<IRQStub
+      	ldx	#>IRQStub
+      	sei
+      	sta	IRQVec
+      	stx	IRQVec+1
+      	cli
+
 ; Pass an empty command line
 
-       	jsr    	push0		; argc
+NoIRQ1: jsr    	push0		; argc
 	jsr	push0		; argv
 
 	ldy	#4    		; Argument size
        	jsr    	_main 		; call the users code
 
-; Call module destructors. This is also the _exit entry.
+; Back from main (this is also the _exit entry). Reset the IRQ vector if
+; we chained it.
 
-_exit:	jsr	donelib		; Run module destructors
+_exit:  lda     #<__IRQFUNC_COUNT__
+	beq	NoIRQ2
+	lda	IRQInd+1
+	ldx	IRQInd+2
+	sei
+	sta	IRQVec
+	stx	IRQVec+1
+	cli
+
+; Run module destructors.
+
+NoIRQ2:	jsr	donelib	 	; Run module destructors
 
 ; Restore system stuff
 
@@ -118,29 +152,65 @@ IRQ:    pha
         pha
         tsx                     ; Get the stack pointer
         lda     $0103,x         ; Get the saved status register
-        tax
-        lda     #>irqret        ; Push new return address
+        tax                     ; Save for later
+        and     #$10            ; Test for BRK bit
+        bne     dobreak
+        lda     #>irq_ret       ; Push new return address
         pha
-        lda     #<irqret
+        lda     #<irq_ret
         pha
         txa
         pha
         sta     ENABLE_ROM      ; Switch to ROM
         jmp     ($FFFE)         ; Jump to kernal irq handler
 
-irqret: sta     ENABLE_RAM      ; Switch back to RAM
+irq_ret:
+        sta     ENABLE_RAM      ; Switch back to RAM
         pla
         tax
         pla
         rti
 
+dobreak:
+        lda     brk_jmp+2       ; Check high byte of address
+        beq     nohandler
+        jmp     brk_jmp         ; Jump to the handler
+
+; No break handler installed, jump to ROM
+
+nohandler:
+        tya
+        pha                     ; ROM handler expects Y on stack
+        sta     ENABLE_ROM
+        jmp     (BRKVec)        ; Jump indirect to the break vector
+
+; ------------------------------------------------------------------------
+; Stub for the IRQ chain. Is used only if there are IRQs defined. Needed in
+; low memory because of the banking.
+
+.segment        "LOWCODE"
+
+IRQStub:
+        cld                     ; Just to be sure
+        sta     ENABLE_RAM      ; Switch to RAM
+	ldy 	#<(__IRQFUNC_COUNT__*2)
+       	lda    	#<__IRQFUNC_TABLE__
+	ldx 	#>__IRQFUNC_TABLE__
+	jsr	condes 		   	; Call the IRQ functions
+	sta    	ENABLE_ROM
+       	jmp    	IRQInd			; Jump to the saved IRQ vector
+
 ; ------------------------------------------------------------------------
 ; Data
 
 .data
-zpsave:	.res	zpspace
+zpsave:	        .res	zpspace
+
+; BRK handling
+brk_jmp:        jmp     $0000
 
 .bss
-spsave:	.res	1
+spsave:	        .res	1
+
 
 
diff --git a/libsrc/plus4/plus4.inc b/libsrc/plus4/plus4.inc
index 680a9611a..b1d67d00f 100644
--- a/libsrc/plus4/plus4.inc
+++ b/libsrc/plus4/plus4.inc
@@ -70,7 +70,7 @@ TED_RAMSEL	= $FF3F
 ; ---------------------------------------------------------------------------
 ; RAM/ROM selection addresses
 
-ENABLE_ROM      = $FF3E
-ENABLE_RAM      = $FF3F
+ENABLE_ROM      = TED_ROMSEL
+ENABLE_RAM      = TED_RAMSEL
 
 
-- 
2.39.5