Added an interrupt facility similar to that on the C128 and Plus/4

git-svn-id: svn://svn.cc65.org/cc65/trunk@2956 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/c64/crt0.s

@@ -5,10 +5,11 @@
 ;
 
 	.export		_exit
-	.import		initlib, donelib
+	.import		initlib, donelib, condes
        	.import	       	zerobss, push0
 	.import	     	callmain
         .import         RESTOR, BSOUT, CLRCH
+	.import	       	__IRQFUNC_TABLE__, __IRQFUNC_COUNT__
 	.import		__RAM_START__, __RAM_SIZE__	; Linker generated
 
         .include        "zeropage.inc"
@@ -76,21 +77,48 @@ 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
+
 ; Push arguments and call main
 
-        jsr     callmain
+NoIRQ1: jsr     callmain
 
-; 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: 	pha			; Save the return code
-	jsr	donelib		; Run module destructors
+_exit: 	pha  			; Save the return code on stack
+	lda     #<__IRQFUNC_COUNT__
+	beq	NoIRQ2
+	lda	IRQInd+1
+	ldx	IRQInd+2
+	sei
+	sta	IRQVec
+	stx	IRQVec+1
+	cli
+
+; Run module destructors
+
+NoIRQ2: jsr	donelib
 
 ; Copy back the zero page stuff
 
        	ldx	#zpspace-1
-L2:	lda	zpsave,x
-	sta	sp,x
-	dex
+L2:   	lda	zpsave,x
+      	sta	sp,x
+      	dex
        	bpl	L2
 
 ; Place the program return code into ST
@@ -109,6 +137,16 @@ L2:	lda	zpsave,x
 
 	jmp	RESTOR
 
+; ------------------------------------------------------------------------
+; The IRQ vector jumps here, if condes routines are defined with type 2.
+
+IRQStub:
+	cld    	       		   	; Just to be sure
+	ldy 	#<(__IRQFUNC_COUNT__*2)
+       	lda    	#<__IRQFUNC_TABLE__
+	ldx 	#>__IRQFUNC_TABLE__
+	jsr	condes 		   	; Call the functions
+       	jmp    	IRQInd			; Jump to the saved IRQ vector
 
 ; ------------------------------------------------------------------------
 ; Data
@@ -116,6 +154,7 @@ L2:	lda	zpsave,x
 .data
 
 zpsave:	.res	zpspace
+IRQInd: jmp     $0000
 
 .bss
 

src/ld65/cfg/c64.cfg

@@ -20,6 +20,11 @@ FEATURES {
 	    type = destructor,
 	    label = __DESTRUCTOR_TABLE__,
 	    count = __DESTRUCTOR_COUNT__;
+    # condes functions with type 2 are called in the interrupt
+    CONDES: segment = RODATA,
+	    type = 2,
+	    label = __IRQFUNC_TABLE__,
+	    count = __IRQFUNC_COUNT__;
 }
 SYMBOLS {
     __STACKSIZE__ = $800;	# 2K stack