From b03db5fdf9d84b152dd2ffbf0a2eb2ad7de43430 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 19 May 2026 16:32:43 -0400
Subject: [PATCH] Attach NMI and HALT.

---
 Components/1770/1770.hpp               | 8 ++++----
 Machines/Tandy/CoCo/CoCo.cpp           | 8 +++++++-
 Machines/Tandy/CoCo/DiskController.cpp | 9 +++++++++
 Machines/Tandy/CoCo/DiskController.hpp | 6 ++++++
 4 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/Components/1770/1770.hpp b/Components/1770/1770.hpp
index caad49d6c..87ea67366 100644
--- a/Components/1770/1770.hpp
+++ b/Components/1770/1770.hpp
@@ -63,15 +63,15 @@ public:
 	};
 
 	/// @returns The current value of the IRQ line output.
-	inline bool get_interrupt_request_line() const	{	return status_.interrupt_request;	}
+	inline bool get_interrupt_request_line() const		{	return status_.interrupt_request;	}
 
 	/// @returns The current value of the DRQ line output.
-	inline bool get_data_request_line() const		{	return status_.data_request;		}
+	inline bool get_data_request_line() const			{	return status_.data_request;		}
 
 	struct Delegate {
 		virtual void wd1770_did_change_output(WD1770 &) = 0;
 	};
-	inline void set_delegate(Delegate *delegate)	{	delegate_ = delegate;				}
+	inline void set_delegate(Delegate *const delegate)	{	delegate_ = delegate;				}
 
 	ClockingHint::Preference preferred_clocking() const final;
 
@@ -127,7 +127,7 @@ private:
 		IndexHoleTarget	= (1 << 6),	// Indicates that index_hole_count_ has reached index_hole_count_target_.
 		ForceInterrupt	= (1 << 7)	// Indicates a forced interrupt.
 	};
-	void posit_event(int type);
+	void posit_event(int);
 	int interesting_event_mask_;
 	Cycles::IntType delay_time_ = 0;
 
diff --git a/Machines/Tandy/CoCo/CoCo.cpp b/Machines/Tandy/CoCo/CoCo.cpp
index f1e6e30b7..46016489e 100644
--- a/Machines/Tandy/CoCo/CoCo.cpp
+++ b/Machines/Tandy/CoCo/CoCo.cpp
@@ -387,7 +387,8 @@ class ConcreteMachine:
 	public MachineTypes::MediaTarget,
 	public MachineTypes::ScanProducer,
 	public MachineTypes::TimedMachine,
-	public Utility::TypeRecipient<Tandy::CoCo::Keyboard::CharacterMapper>
+	public Utility::TypeRecipient<Tandy::CoCo::Keyboard::CharacterMapper>,
+	public WD::WD1770::Delegate
 {
 public:
 	ConcreteMachine(const Analyser::Static::TandyCoCo::Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
@@ -453,6 +454,7 @@ public:
 
 		if(has_disk_drive) {
 			sam_.insert_cartridge(roms.find(DiskBASIC)->second);
+			disk_controller_.set_delegate(this);
 		}
 
 		insert_media(target.media);
@@ -1109,6 +1111,10 @@ private:
 
 	DiskController disk_controller_;
 	Cycles cycles_16mhz_;
+	void wd1770_did_change_output(WD::WD1770 &) override {
+		m6809_.template set<CPU::M6809::Line::NMI>(disk_controller_.nmi());
+		m6809_.template set<CPU::M6809::Line::Halt>(disk_controller_.halt());
+	}
 };
 
 }
diff --git a/Machines/Tandy/CoCo/DiskController.cpp b/Machines/Tandy/CoCo/DiskController.cpp
index f4344d044..1347cc54e 100644
--- a/Machines/Tandy/CoCo/DiskController.cpp
+++ b/Machines/Tandy/CoCo/DiskController.cpp
@@ -24,6 +24,7 @@ void DiskController::set_control(const uint8_t value) {
 	//	b3: drive motors, 1 = on
 	//	b0–b2: drive selects
 
+	double_density_ = value & 0x20;
 	set_is_double_density(value & 0x20);
 	for_all_drives([&] (Storage::Disk::Drive &drive, size_t) {
 		drive.set_motor_on(value & 0x8);
@@ -60,3 +61,11 @@ const Storage::Disk::Disk *DiskController::disk(const std::string &name) {
 //	* not INTRQ hits a NOR gate with DDEN; NOR of that is piped to NMI; and
 //	* DRQ informs HALT, if enabled.
 //
+
+bool DiskController::halt() const {
+	return get_data_request_line();
+}
+
+bool DiskController::nmi() const {
+	return get_interrupt_request_line() && double_density_;
+}
diff --git a/Machines/Tandy/CoCo/DiskController.hpp b/Machines/Tandy/CoCo/DiskController.hpp
index 423443c8c..500da0d0c 100644
--- a/Machines/Tandy/CoCo/DiskController.hpp
+++ b/Machines/Tandy/CoCo/DiskController.hpp
@@ -42,6 +42,12 @@ public:
 	void set_activity_observer(Activity::Observer *);
 	void set_disk(std::shared_ptr<Storage::Disk::Disk>, size_t drive);
 	const Storage::Disk::Disk *disk(const std::string &);
+
+	bool halt() const;
+	bool nmi() const;
+
+private:
+	bool double_density_ = false;
 };
 
 }