From 211e5f544d3f45242503c58944b16cd62646f72b Mon Sep 17 00:00:00 2001
From: MetalliC <0vetal0@gmail.com>
Date: Fri, 9 Sep 2016 12:41:12 +0300
Subject: [PATCH] sms.cpp: more accurate FM Sound Unit behavior [Enik Land]

---
 src/devices/bus/sg1000_exp/fm_unit.cpp | 16 +++++++++++++---
 src/mame/drivers/sms.cpp               | 17 ++++++++++++++---
 src/mame/machine/sms.cpp               |  2 +-
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/src/devices/bus/sg1000_exp/fm_unit.cpp b/src/devices/bus/sg1000_exp/fm_unit.cpp
index 46e7b036704..da3759ca26f 100644
--- a/src/devices/bus/sg1000_exp/fm_unit.cpp
+++ b/src/devices/bus/sg1000_exp/fm_unit.cpp
@@ -9,6 +9,15 @@ Release data from the Sega Retro project:
 
   Year: 1987    Country/region: JP    Model code: FM-70
 
+Notes:
+
+This emulation is based on Charles MacDonald's analysis of Enri's schematics
+of the FM unit hardware.
+
+Any software that access controllers through IO ports $C0/$C1 instead $DC/$DD
+(the game Fushigi no Oshiro Pit Pot is a known example) has control problems
+when the FM Sound Unit is attached (real hardware behavior).
+
 **********************************************************************/
 
 #include "fm_unit.h"
@@ -69,7 +78,7 @@ void sega_fm_unit_device::device_start()
 
 READ8_MEMBER(sega_fm_unit_device::peripheral_r)
 {
-	if (offset == 2)
+	if (offset <= 3)
 	{
 		return m_audio_control & 0x01;
 	}
@@ -98,6 +107,7 @@ WRITE8_MEMBER(sega_fm_unit_device::peripheral_w)
 			}
 			break;
 		case 2: // control port
+		case 3: // mirror
 			m_audio_control = data & 0x01;
 			break;
 		default:
@@ -108,11 +118,11 @@ WRITE8_MEMBER(sega_fm_unit_device::peripheral_w)
 
 bool sega_fm_unit_device::is_readable(UINT8 offset)
 {
-	return (offset == 2) ? true : false;
+	return (offset <= 3) ? true : false;
 }
 
 
 bool sega_fm_unit_device::is_writeable(UINT8 offset)
 {
-	return (offset <= 2) ? true : false;
+	return (offset <= 3) ? true : false;
 }
diff --git a/src/mame/drivers/sms.cpp b/src/mame/drivers/sms.cpp
index 937b714c4dd..2f12aedb724 100644
--- a/src/mame/drivers/sms.cpp
+++ b/src/mame/drivers/sms.cpp
@@ -870,8 +870,15 @@ static MACHINE_CONFIG_DERIVED( sms1_kr, sms1_ntsc )
 	MCFG_CPU_MODIFY("maincpu")
 	MCFG_CPU_IO_MAP(smskr_io)
 
+	// need to replace the cartridge slot with the Japanese version, so to
+	// keep the usual media order, remove and reinsert all of them.
 	MCFG_DEVICE_REMOVE("slot")
+	MCFG_DEVICE_REMOVE("mycard")
+	MCFG_DEVICE_REMOVE("smsexp")
 	MCFG_SG1000MK3_CARTRIDGE_ADD("slot", sg1000mk3_cart, nullptr)
+	MCFG_SMS_CARD_ADD("mycard", sms_cart, nullptr)
+	MCFG_SMS_EXPANSION_ADD("smsexp", sms_expansion_devices, nullptr)
+
 	MCFG_SOFTWARE_LIST_ADD("cart_list2","sg1000")
 
 	MCFG_DEVICE_MODIFY("sms_vdp")
@@ -890,13 +897,17 @@ static MACHINE_CONFIG_DERIVED( sg1000m3, sms1_ntsc )
 	MCFG_CPU_MODIFY("maincpu")
 	MCFG_CPU_IO_MAP(sg1000m3_io)
 
+	// Remove and reinsert all media slots, as done with the sms1_kr config,
+	// and also replace the expansion slot with the SG-1000 version.
 	MCFG_DEVICE_REMOVE("slot")
-	MCFG_SG1000MK3_CARTRIDGE_ADD("slot", sg1000mk3_cart, nullptr)
-	MCFG_SOFTWARE_LIST_ADD("cart_list2","sg1000")
-
+	MCFG_DEVICE_REMOVE("mycard")
 	MCFG_DEVICE_REMOVE("smsexp")
+	MCFG_SG1000MK3_CARTRIDGE_ADD("slot", sg1000mk3_cart, nullptr)
+	MCFG_SMS_CARD_ADD("mycard", sms_cart, nullptr)
 	MCFG_SG1000_EXPANSION_ADD("sgexp", sg1000_expansion_devices, nullptr, false)
 
+	MCFG_SOFTWARE_LIST_ADD("cart_list2","sg1000")
+
 	// Mark III does not have TH connected.
 	MCFG_SMS_CONTROL_PORT_MODIFY(CONTROL1_TAG)
 	MCFG_SMS_CONTROL_PORT_TH_INPUT_HANDLER(NOOP)
diff --git a/src/mame/machine/sms.cpp b/src/mame/machine/sms.cpp
index 094a8aaa721..a268aa4d936 100644
--- a/src/mame/machine/sms.cpp
+++ b/src/mame/machine/sms.cpp
@@ -287,7 +287,7 @@ WRITE_LINE_MEMBER(sms_state::sms_csync_callback)
 		{
 			// Timings for Rapid Fire and LED verified by Charles MacDonald.
 
-			// Read state is changed at each 256 C-Sync pulses
+			// Read state is probably changed at each 256 C-Sync pulses
 			if ((m_csync_counter & 0xff) == 0)
 			{
 				m_rapid_read_state ^= 0xff;