From 04d24d5368efc44da441a43159249862ee5853ce Mon Sep 17 00:00:00 2001
From: Patrick Mackinlay <pmackinlay@hotmail.com>
Date: Fri, 24 Mar 2023 17:24:39 +0700
Subject: mc146818: add ds1397 variant

---
 src/devices/machine/mc146818.cpp | 36 ++++++++++++++++++++++++++++++++++++
 src/devices/machine/mc146818.h   | 18 ++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/src/devices/machine/mc146818.cpp b/src/devices/machine/mc146818.cpp
index f1b7ffa97a0..dbe5ab11051 100644
--- a/src/devices/machine/mc146818.cpp
+++ b/src/devices/machine/mc146818.cpp
@@ -24,6 +24,7 @@
 // device type definition
 DEFINE_DEVICE_TYPE(MC146818, mc146818_device, "mc146818", "MC146818 RTC")
 DEFINE_DEVICE_TYPE(DS1287,   ds1287_device,   "ds1287",   "DS1287 RTC")
+DEFINE_DEVICE_TYPE(DS1397,   ds1397_device,   "ds1397",   "DS1397 RAMified RTC")
 
 //-------------------------------------------------
 //  mc146818_device - constructor
@@ -49,6 +50,11 @@ ds1287_device::ds1287_device(const machine_config &mconfig, const char *tag, dev
 {
 }
 
+ds1397_device::ds1397_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
+	: mc146818_device(mconfig, DS1397, tag, owner, clock)
+{
+}
+
 mc146818_device::mc146818_device(const machine_config &mconfig, device_type type, const char *tag, device_t *owner, uint32_t clock)
 	: device_t(mconfig, type, tag, owner, clock),
 		device_nvram_interface(mconfig, *this),
@@ -721,3 +727,33 @@ void mc146818_device::internal_write(offs_t offset, uint8_t data)
 		break;
 	}
 }
+
+void ds1397_device::device_start()
+{
+	mc146818_device::device_start();
+
+	save_item(NAME(m_xram_page));
+}
+
+void ds1397_device::device_reset()
+{
+	mc146818_device::device_reset();
+
+	m_xram_page = 0;
+}
+
+u8 ds1397_device::xram_r(offs_t offset)
+{
+	if (offset < 0x20)
+		return m_data[0x40 + m_xram_page * 0x20 + offset];
+	else
+		return m_xram_page;
+}
+
+void ds1397_device::xram_w(offs_t offset, u8 data)
+{
+	if (offset < 0x20)
+		m_data[0x40 + m_xram_page * 0x20 + offset] = data;
+	else
+		m_xram_page = data & 0x7f;
+}
diff --git a/src/devices/machine/mc146818.h b/src/devices/machine/mc146818.h
index b352c2894e8..6e3fff11fd7 100644
--- a/src/devices/machine/mc146818.h
+++ b/src/devices/machine/mc146818.h
@@ -181,8 +181,26 @@ public:
 	ds1287_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 };
 
+class ds1397_device : public mc146818_device
+{
+public:
+	ds1397_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+
+	virtual void device_start() override;
+	virtual void device_reset() override;
+
+	u8 xram_r(offs_t offset);
+	void xram_w(offs_t offset, u8 data);
+
+protected:
+	virtual int data_size() const override { return 64 + 4096; }
+
+	u8 m_xram_page;
+};
+
 // device type definition
 DECLARE_DEVICE_TYPE(MC146818, mc146818_device)
 DECLARE_DEVICE_TYPE(DS1287, ds1287_device)
+DECLARE_DEVICE_TYPE(DS1397, ds1397_device)
 
 #endif // MAME_MACHINE_MC146818_H
-- 
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