New target c16

git-svn-id: svn://svn.cc65.org/cc65/trunk@1563 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/c16/break.s

@@ -0,0 +1,108 @@
+;
+; Ullrich von Bassewitz, 27.09.1998
+;
+; void set_brk (unsigned Addr);
+; void reset_brk (void);
+;
+
+       	.export	   	_set_brk, _reset_brk
+	.destructor	_reset_brk
+	.export	       	_brk_a, _brk_x, _brk_y, _brk_sr, _brk_pc
+
+	.include      	"../plus4/plus4.inc"
+
+
+.bss
+_brk_a:		.res	1
+_brk_x:		.res   	1
+_brk_y:		.res   	1
+_brk_sr:	.res	1
+_brk_pc:	.res	2
+
+oldvec:       	.res	2   		; Old vector
+
+
+.data
+uservec:    	jmp	$FFFF		; Patched at runtime
+
+
+.code
+
+; Set the break vector
+.proc	_set_brk
+
+	sta	uservec+1
+  	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
+	rts
+
+.endproc
+
+
+; 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	#$00
+	sta	oldvec		; Clear the old vector
+	stx	oldvec+1
+@L9:	rts
+
+.endproc
+
+
+
+; Break handler, called if a break occurs
+
+.proc	brk_handler
+
+	pla
+	sta	_brk_y
+	pla
+	sta	_brk_x
+	pla
+	sta	_brk_a
+	pla
+	and	#$EF		; Clear break bit
+	sta	_brk_sr
+	pla	    		; PC low
+	sec
+	sbc	#2 		; Point to start of brk
+	sta	_brk_pc
+	pla	    		; PC high
+	sbc	#0
+	sta	_brk_pc+1
+
+	jsr	uservec		; Call the user's routine
+
+	lda	_brk_pc+1
+	pha
+	lda	_brk_pc
+	pha
+	lda	_brk_sr
+	pha
+	ldx    	_brk_x
+	ldy	_brk_y
+	lda	_brk_a
+	rti	   		; Jump back...
+
+.endproc
+
+