From 8cd1575891b4a221433fe814af2ac67ea8feceb5 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 28 Dec 2016 18:52:36 -0500
Subject: [PATCH] Similar fix to that over in Oric land: ensure a known,
 effective initial value for the Plus 3's control register.

---
 Machines/Electron/Plus3.cpp | 9 ++++++++-
 Machines/Electron/Plus3.hpp | 1 +
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/Machines/Electron/Plus3.cpp b/Machines/Electron/Plus3.cpp
index 9100a860c..d026f6bf9 100644
--- a/Machines/Electron/Plus3.cpp
+++ b/Machines/Electron/Plus3.cpp
@@ -10,7 +10,10 @@
 
 using namespace Electron;
 
-Plus3::Plus3() : WD1770(P1770) {}
+Plus3::Plus3() : WD1770(P1770), last_control_(0)
+{
+	set_control_register(last_control_, 0xff);
+}
 
 void Plus3::set_disk(std::shared_ptr<Storage::Disk::Disk> disk, int drive)
 {
@@ -31,7 +34,11 @@ void Plus3::set_control_register(uint8_t control)
 
 	uint8_t changes = control ^ last_control_;
 	last_control_ = control;
+	set_control_register(control, changes);
+}
 
+void Plus3::set_control_register(uint8_t control, uint8_t changes)
+{
 	if(changes&3)
 	{
 		switch(control&3)
diff --git a/Machines/Electron/Plus3.hpp b/Machines/Electron/Plus3.hpp
index 8e6b7c0e4..37cf5b324 100644
--- a/Machines/Electron/Plus3.hpp
+++ b/Machines/Electron/Plus3.hpp
@@ -21,6 +21,7 @@ class Plus3 : public WD::WD1770 {
 		void set_control_register(uint8_t control);
 
 	private:
+		void set_control_register(uint8_t control, uint8_t changes);
 		std::shared_ptr<Storage::Disk::Drive> drives_[2];
 		int selected_drive_;
 		uint8_t last_control_;