From ab7af50b132498aabb58022f55ee07ce0b77bd82 Mon Sep 17 00:00:00 2001
From: yz70s <yz70s@users.noreply.github.com>
Date: Fri, 4 Jan 2019 20:30:21 +0100
Subject: [PATCH] ds128x.cpp: add device ds12885ext same as ds12885 but 256
 bytes ram (nw)

---
 src/devices/machine/ds128x.cpp | 58 +++++++++++++++++++++++++++++++++-
 src/devices/machine/ds128x.h   | 25 ++++++++++++++-
 2 files changed, 81 insertions(+), 2 deletions(-)

diff --git a/src/devices/machine/ds128x.cpp b/src/devices/machine/ds128x.cpp
index 7a397aab303..a234e3abf82 100644
--- a/src/devices/machine/ds128x.cpp
+++ b/src/devices/machine/ds128x.cpp
@@ -10,7 +10,12 @@ DEFINE_DEVICE_TYPE(DS12885, ds12885_device, "ds12885", "DS12885 RTC/NVRAM")
 //-------------------------------------------------
 
 ds12885_device::ds12885_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
-	: mc146818_device(mconfig, DS12885, tag, owner, clock)
+	: ds12885_device(mconfig, DS12885, tag, owner, clock)
+{
+}
+
+ds12885_device::ds12885_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock)
+	: mc146818_device(mconfig, type, tag, owner, clock)
 {
 }
 
@@ -23,3 +28,54 @@ int ds12885_device::get_timer_bypass()
 
 	return 22; // No tick
 }
+
+DEFINE_DEVICE_TYPE(DS12885EXT, ds12885ext_device, "ds12885ext", "DS12885 RTC/NVRAM size 256 bytes")
+
+//-------------------------------------------------
+//  ds12885ext_device - constructor
+//-------------------------------------------------
+
+ds12885ext_device::ds12885ext_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
+	: ds12885_device(mconfig, DS12885EXT, tag, owner, clock)
+{
+}
+
+//-------------------------------------------------
+//  ds12885ext_device - handlers that allow acces to extended memory size
+//-------------------------------------------------
+
+READ8_MEMBER(ds12885ext_device::read_extended)
+{
+	switch (offset)
+	{
+	case 0:
+	case 1:
+		return read(space, offset, mem_mask);
+		break;
+	case 2:
+	case 3:
+		return read(space, offset - 2, mem_mask);
+		break;
+	default:
+		return 0xff;
+	}
+}
+
+WRITE8_MEMBER(ds12885ext_device::write_extended)
+{
+	switch (offset)
+	{
+	case 0:
+		write(space, offset, data & 127, mem_mask);
+		break;
+	case 1:
+		write(space, offset, data, mem_mask);
+		break;
+	case 2:
+		write(space, offset - 2, data, mem_mask);
+		break;
+	case 3:
+		write(space, offset - 2, data, mem_mask);
+		break;
+	}
+}
diff --git a/src/devices/machine/ds128x.h b/src/devices/machine/ds128x.h
index 671d3ee0a6f..5f5e4016000 100644
--- a/src/devices/machine/ds128x.h
+++ b/src/devices/machine/ds128x.h
@@ -8,13 +8,17 @@
 #define MCFG_DS12885_ADD(_tag) \
 	MCFG_DEVICE_ADD(_tag, DS12885, XTAL(32'768))
 
-// ======================> mc146818_device
+#define MCFG_DS12885EXT_ADD(_tag) \
+	MCFG_DEVICE_ADD(_tag, DS12885EXT, XTAL(32'768))
+
+// ======================> ds12885_device
 
 class ds12885_device : public mc146818_device
 {
 public:
 	// construction/destruction
 	ds12885_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock = 32'768);
+	ds12885_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock = 32'768);
 
 protected:
 	virtual int data_size() override { return 128; }
@@ -24,4 +28,23 @@ protected:
 // device type definition
 DECLARE_DEVICE_TYPE(DS12885, ds12885_device)
 
+// ======================> ds12885ext_device
+
+class ds12885ext_device : public ds12885_device
+{
+public:
+	// construction/destruction
+	ds12885ext_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock = 32'768);
+
+	// read/write access to extended ram
+	DECLARE_READ8_MEMBER(read_extended);
+	DECLARE_WRITE8_MEMBER(write_extended);
+
+protected:
+	virtual int data_size() override { return 256; }
+};
+
+// device type definition
+DECLARE_DEVICE_TYPE(DS12885EXT, ds12885ext_device)
+
 #endif // MAME_MACHINE_DS128X_H