From a877bb053b821c32320a0ef651b96bb83ab34d79 Mon Sep 17 00:00:00 2001
From: Dirk Best <mail@dirk-best.de>
Date: Wed, 20 May 2015 15:59:11 +0200
Subject: [PATCH] nascom_fdc: proper support for single/double sided disk
 drives

---
 src/emu/bus/nasbus/floppy.c | 51 +++++++++++++++++++++++++++++++++++--
 src/emu/bus/nasbus/floppy.h |  7 ++---
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/src/emu/bus/nasbus/floppy.c b/src/emu/bus/nasbus/floppy.c
index 5eebd9a10c6..f140ff9ab0a 100644
--- a/src/emu/bus/nasbus/floppy.c
+++ b/src/emu/bus/nasbus/floppy.c
@@ -10,6 +10,14 @@
 #include "formats/nascom_dsk.h"
 
 
+//**************************************************************************
+//  CONSTANTS/MACROS
+//**************************************************************************
+
+#define VERBOSE 1
+#define VERBOSE_STATUS 0
+
+
 //**************************************************************************
 //  DEVICE DEFINITIONS
 //**************************************************************************
@@ -88,6 +96,22 @@ void nascom_fdc_device::device_reset()
 	m_nasbus->m_io->install_read_handler(0xe5, 0xe5, read8_delegate(FUNC(nascom_fdc_device::status_r), this));
 }
 
+//-------------------------------------------------
+//  device_reset_after_children - device-specific reset after children
+//-------------------------------------------------
+
+void nascom_fdc_device::device_reset_after_children()
+{
+	// sanity check
+	if (m_floppy0->get_device() && m_floppy1->get_device())
+		if (m_floppy0->get_device()->get_sides() != m_floppy1->get_device()->get_sides())
+			fatalerror("Floppy drive 0 and 1 need to be of the same type.\n");
+
+	if (m_floppy2->get_device() && m_floppy3->get_device())
+		if (m_floppy2->get_device()->get_sides() != m_floppy3->get_device()->get_sides())
+			fatalerror("Floppy drive 2 and 3 need to be of the same type.\n");
+}
+
 
 //**************************************************************************
 //  IMPLEMENTATION
@@ -95,12 +119,32 @@ void nascom_fdc_device::device_reset()
 
 READ8_MEMBER( nascom_fdc_device::select_r )
 {
-	return m_select | 0xa0;
+	m_select |= (0x80 | 0x20);
+
+	// double sided drive for drive 0/1?
+	if (m_floppy0->get_device() && (m_floppy0->get_device()->get_sides() == 2))
+		m_select &= ~0x20;
+
+	if (m_floppy1->get_device() && (m_floppy1->get_device()->get_sides() == 2))
+		m_select &= ~0x20;
+
+	// double sided drive for drive 2/3?
+	if (m_floppy2->get_device() && (m_floppy2->get_device()->get_sides() == 2))
+		m_select &= ~0x80;
+
+	if (m_floppy3->get_device() && (m_floppy3->get_device()->get_sides() == 2))
+		m_select &= ~0x80;
+
+	if (VERBOSE)
+		logerror("nascom_fdc_device::select_r: 0x%02x\n", m_select);
+
+	return m_select;
 }
 
 WRITE8_MEMBER( nascom_fdc_device::select_w )
 {
-	logerror("nascom_fdc_device::select_w: 0x%02x\n", data);
+	if (VERBOSE)
+		logerror("nascom_fdc_device::select_w: 0x%02x\n", data);
 
 	m_floppy = NULL;
 
@@ -129,5 +173,8 @@ READ8_MEMBER( nascom_fdc_device::status_r )
 	data |= m_fdc->intrq_r() << 0;
 	data |= m_fdc->drq_r()   << 7;
 
+	if (VERBOSE_STATUS)
+		logerror("nascom_fdc_device::status_r: 0x%02x\n", data);
+
 	return data;
 }
diff --git a/src/emu/bus/nasbus/floppy.h b/src/emu/bus/nasbus/floppy.h
index 5bedb37a7e4..6994a9e978f 100644
--- a/src/emu/bus/nasbus/floppy.h
+++ b/src/emu/bus/nasbus/floppy.h
@@ -28,9 +28,9 @@ public:
 	// construction/destruction
 	nascom_fdc_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock);
 
-	DECLARE_READ8_MEMBER( select_r );
-	DECLARE_WRITE8_MEMBER( select_w );
-	DECLARE_READ8_MEMBER( status_r );
+	DECLARE_READ8_MEMBER(select_r);
+	DECLARE_WRITE8_MEMBER(select_w);
+	DECLARE_READ8_MEMBER(status_r);
 
 	DECLARE_FLOPPY_FORMATS(floppy_formats);
 
@@ -38,6 +38,7 @@ protected:
 	virtual machine_config_constructor device_mconfig_additions() const;
 	virtual void device_start();
 	virtual void device_reset();
+	virtual void device_reset_after_children();
 
 private:
 	required_device<fd1793_t> m_fdc;