From 4c7a15f524aabce1103f9b9857af6b936193aa4f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rados=C5=82aw=20Kujawa?= <radoslaw.kujawa@c0ff33.net>
Date: Thu, 9 Feb 2017 21:53:45 +0100
Subject: [PATCH] Add emulation of WAI instruction.

---
 src/65c02isa.csv |  2 +-
 src/emulation.c  |  8 ++++++++
 src/rk65c02.c    | 21 ++++++++++++++++++++-
 src/rk65c02.h    |  1 +
 4 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/65c02isa.csv b/src/65c02isa.csv
index ab9d42d..9444b97 100644
--- a/src/65c02isa.csv
+++ b/src/65c02isa.csv
@@ -202,7 +202,7 @@ OP_SMB4_ZP,"smb4",ZP,2,emul_smb4,false
 OP_INY,"iny",IMPLIED,1,emul_iny,false
 OP_CMP_IMM,"cmp",IMMEDIATE,2,emul_cmp,false
 OP_DEX,"dex",IMPLIED,1,emul_dex,false
-OP_WAI,"wai",IMPLIED,1,NULL,false
+OP_WAI,"wai",IMPLIED,1,emul_wai,false
 OP_CPY_ABS,"cpy",ABSOLUTE,3,emul_cpy,false
 OP_CMP_ABS,"cmp",ABSOLUTE,3,emul_cmp,false
 OP_DEC_ABS,"dec",ABSOLUTE,3,emul_dec,false
diff --git a/src/emulation.c b/src/emulation.c
index 710e41b..d47d18f 100644
--- a/src/emulation.c
+++ b/src/emulation.c
@@ -1014,3 +1014,11 @@ emul_tya(rk65c02emu_t *e, void *id, instruction_t *i)
 	instruction_status_adjust_negative(e, e->regs.A);
 }
 
+/* WAI - wait for interrupt */
+void
+emul_wai(rk65c02emu_t *e, void *id, instruction_t *i)
+{
+	e->state = STOPPED;
+	e->stopreason = WAI;
+}
+
diff --git a/src/rk65c02.c b/src/rk65c02.c
index f01d784..0226fdc 100644
--- a/src/rk65c02.c
+++ b/src/rk65c02.c
@@ -22,6 +22,7 @@ rk65c02_init(bus_t *b)
 
 	e.bus = b;
 	e.state = STOPPED;
+	e.stopreason = HOST;
 	e.regs.P = P_UNDEFINED|P_IRQ_DISABLE;
 	/* reset also clears the decimal flag */
 	e.regs.P &= ~P_DECIMAL;
@@ -32,7 +33,25 @@ rk65c02_init(bus_t *b)
 }
 
 /*
- * Do interrupt'ey things and start the interrupt service routine.
+ * Assert the IRQ line.
+ */
+void
+rk65c02_assert_irq(rk65c02emu_t *e)
+{
+	/* 
+	 * Clearly this is too simpleton'ish, because more than one device
+	 * might want to assert the interrupt line (on hardware level it is
+	 * active low, so can just be pulled down by any device connected
+	 * to it.
+	 */
+	e->irq = true;
+
+	if ((e->state == STOPPED) && (e->stopreason == WAI))
+		rk65c02_start(e);
+}
+
+/*
+ * Respond to interrupt and start the interrupt service routine.
  */
 void
 rk65c02_irq(rk65c02emu_t *e)
diff --git a/src/rk65c02.h b/src/rk65c02.h
index a2c9bd4..4f9c52f 100644
--- a/src/rk65c02.h
+++ b/src/rk65c02.h
@@ -11,6 +11,7 @@ typedef enum {
 
 typedef enum {
 	STP,		/* due to 65C02 STP instruction */
+	WAI,		/* waiting for interrupt */
 	BREAKPOINT,	/* due to breakpoint set */
 	WATCHPOINT,	/* due to watchpoint set */
 	STEPPED,	/* stepped appropriate number of instructions */