From c72bdd776e4816aa5a2f78a1491dfe2f417c86e3 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 7 Dec 2020 22:43:24 -0500
Subject: [PATCH] Adds a new assert: I think this is the issue getting into
 GS/OS.

---
 Processors/65816/Implementation/65816Implementation.hpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Processors/65816/Implementation/65816Implementation.hpp b/Processors/65816/Implementation/65816Implementation.hpp
index 878be5e92..0a910f158 100644
--- a/Processors/65816/Implementation/65816Implementation.hpp
+++ b/Processors/65816/Implementation/65816Implementation.hpp
@@ -419,6 +419,9 @@ template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler,
 						pending_exceptions_ &= ~NMI;
 						data_address_ = registers_.emulation_flag ? 0xfffa : 0xffea;
 					} else if(pending_exceptions_ & IRQ & registers_.flags.inverse_interrupt) {
+						// TODO: this isn't a correct way to handle usurption, I think;
+						// if an IRQ was selected for servicing I think it'll now be servied
+						// even if the IRQ line has gone low in the interim.
 						pending_exceptions_ &= ~IRQ;
 						data_address_ = registers_.emulation_flag ? 0xfffe : 0xffee;
 					} else if(pending_exceptions_ & Abort) {
@@ -428,6 +431,9 @@ template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler,
 						pending_exceptions_ &= ~Abort;
 						data_address_ = registers_.emulation_flag ? 0xfff8 : 0xffe8;;
 					} else {
+						// Test that this really is BRK or COP.
+						assert((active_instruction_ == instructions) || (active_instruction_ == &instructions[0x02]));
+
 						is_brk = active_instruction_ == instructions;	// Given that BRK has opcode 00.
 						if(is_brk) {
 							data_address_ = registers_.emulation_flag ? 0xfffe : 0xffe6;