Added enough stuff that SSDs attached to a 1770 will now reach the entry point for writing.

Components/1770/1770.cpp

@@ -498,7 +498,7 @@ void WD1770::posit_event(Event new_event_type)
 		WAIT_FOR_TIME(30);
 
 	test_type2_write_protection:
-		if(command_&0x20) // TODO:: && is_write_protected
+		if(command_&0x20 && get_drive_is_read_only())
 		{
 			update_status([] (Status &status) {
 				status.write_protect = true;

Storage/Disk/DiskController.cpp

@@ -181,6 +181,12 @@ bool Controller::get_drive_is_ready()
 	return drive_->has_disk();
 }
 
+bool Controller::get_drive_is_read_only()
+{
+	if(!drive_) return false;
+	return drive_->get_is_read_only();
+}
+
 void Controller::step(int direction)
 {
 	if(drive_) drive_->step(direction);

Storage/Disk/DiskController.hpp

@@ -99,6 +99,7 @@ class Controller: public DigitalPhaseLockedLoop::Delegate, public TimedEventLoop
 		bool get_is_track_zero();
 		void step(int direction);
 		virtual bool get_drive_is_ready();
+		bool get_drive_is_read_only();
 
 	private:
 		Time bit_length_;

Storage/Disk/Formats/SSD.cpp

@@ -40,6 +40,11 @@ unsigned int SSD::get_head_count()
 	return head_count_;
 }
 
+bool SSD::get_is_read_only()
+{
+	return false;
+}
+
 std::shared_ptr<Track> SSD::get_uncached_track_at_position(unsigned int head, unsigned int position)
 {
 	std::shared_ptr<Track> track;

Storage/Disk/Formats/SSD.hpp

@@ -35,6 +35,7 @@ class SSD: public Disk, public Storage::FileHolder {
 		// implemented to satisfy @c Disk
 		unsigned int get_head_position_count();
 		unsigned int get_head_count();
+		bool get_is_read_only();
 
 	private:
 		std::shared_ptr<Track> get_uncached_track_at_position(unsigned int head, unsigned int position);