From 5df392ff14180b87df886fef1b2fdca6c951f3fc Mon Sep 17 00:00:00 2001
From: "ol.sc" <ol.sc@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Thu, 19 Jan 2012 00:24:13 +0000
Subject: [PATCH] Added wrapper for C level irq handling.

git-svn-id: svn://svn.cc65.org/cc65/trunk@5408 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 include/6502.h            |  18 +++++--
 libsrc/common/Makefile    |   1 +
 libsrc/common/interrupt.s | 102 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+), 3 deletions(-)
 create mode 100644 libsrc/common/interrupt.s

diff --git a/include/6502.h b/include/6502.h
index 08b826800..e0f161f92 100644
--- a/include/6502.h
+++ b/include/6502.h
@@ -100,15 +100,27 @@ typedef void (*brk_handler) (void);
 /* Type of the break handler */
 
 void __fastcall__ set_brk (brk_handler f);
-/* Set the break vector to the given address, return the old address */
+/* Set the break vector to the given address */
 
 void reset_brk (void);
 /* Reset the break vector to the original value */
 
 
 
-/* End of 6502.h */
-#endif
+/* Possible returns for irq_handler() */
+#define IRQ_NOT_HANDLED	0
+#define IRQ_HANDLED	1
+
+typedef unsigned (*irq_handler) (void);
+/* Type of the C level interrupt request handler */
+
+void __fastcall__ set_irq (irq_handler f, void *stack_addr, size_t stack_size);
+/* Set the C level interrupt request vector to the given address */
 
+void reset_irq (void);
+/* Reset the C level interrupt request vector */
 
 
+
+/* End of 6502.h */
+#endif
diff --git a/libsrc/common/Makefile b/libsrc/common/Makefile
index 77a77e990..83966a004 100644
--- a/libsrc/common/Makefile
+++ b/libsrc/common/Makefile
@@ -123,6 +123,7 @@ S_OBJS = 	_cwd.o                  \
 		getcpu.o	        \
                 getcwd.o                \
 		getenv.o	        \
+		interrupt.o	        \
 		isalnum.o	        \
 		isalpha.o	        \
 		isblank.o	        \
diff --git a/libsrc/common/interrupt.s b/libsrc/common/interrupt.s
new file mode 100644
index 000000000..0b05ed820
--- /dev/null
+++ b/libsrc/common/interrupt.s
@@ -0,0 +1,102 @@
+;
+; Oliver Schmidt, 2012-01-18
+;
+; void __fastcall__ set_irq (irq_handler f, void *stack_addr, size_t stack_size);
+; void reset_irq (void);
+;
+
+	.export	   	_set_irq, _reset_irq
+	.interruptor    clevel_irq, 1		; Export as low priority IRQ handler
+	.import 	popax
+
+	.include        "zeropage.inc"
+
+	.macpack	generic
+
+
+.proc	_set_irq
+
+	; Keep clevel_irq from being called right now
+	sei
+
+	; Set irq stack pointer to stack_addr + stack_size
+	sta	irqsp
+	stx	irqsp+1
+	jsr	popax
+	add	irqsp
+	sta	irqsp
+	txa
+	adc	irqsp+1
+	sta	irqsp+1
+
+	; Set irq vector to irq_handler
+	jsr	popax
+	sta	irqvec+1
+	stx	irqvec+2 	; Set the user vector
+
+	; Restore interrupt requests and return
+	cli
+	rts
+
+.endproc
+
+
+.proc	_reset_irq
+
+	lda  	#$00
+	sta	irqvec+3	; High byte is enough
+	rts
+
+.endproc
+
+
+.proc	clevel_irq
+
+	; Is C level interrupt request vector set?
+	lda	irqvec+3	; High byte is enough
+	bne	@L1
+	clc			; Interrupt not handled
+	rts
+
+	; Save our zero page locations
+@L1:	ldx     #zpspace-1
+@L2:    lda     sp,x
+	sta     zpsave,x
+	dex
+	bpl     @L2
+
+	; Set C level interrupt stack
+	lda	irqsp
+	ldx	irqsp+1
+	sta	sp
+	stx	sp+1
+
+	; Call C level interrupt request handler
+	jsr	irqvec
+	
+	; Copy back our zero page content
+	ldx     #zpspace-1
+@L3:    ldy     zpsave,x
+	sty     sp,x
+	dex
+	bpl     @L3
+
+	; Mark interrupt handled / not handled and return
+	lsr
+	rts
+
+.endproc
+
+; ---------------------------------------------------------------------------
+
+.data
+
+irqvec:	jmp	$00FF		; Patched at runtime
+
+; ---------------------------------------------------------------------------
+
+.bss
+
+irqsp:	.res	2
+
+zpsave: .res    zpspace
-- 
2.39.5