bt450: new ramdac device

scripts/src/video.lua

@@ -1720,3 +1720,15 @@ if (VIDEOS["ZR36110"]~=null) then
 		MAME_DIR .. "src/devices/video/zr36110.h",
 	}
 end
+
+--------------------------------------------------
+--
+--@src/devices/video/bt450.h,VIDEOS["BT450"] = true
+--------------------------------------------------
+
+if (VIDEOS["BT450"]~=null) then
+	files {
+		MAME_DIR .. "src/devices/video/bt450.cpp",
+		MAME_DIR .. "src/devices/video/bt450.h",
+	}
+end

src/devices/video/bt450.cpp

@@ -0,0 +1,99 @@
+// license:BSD-3-Clause
+// copyright-holders:Patrick Mackinlay
+
+/*
+ * Brooktree Bt450 66MHz Monolithic CMOS 16x12 Color Palette RAMDAC
+ *
+ * Sources:
+ *  - Product Databook 1991, Brooktree Corporation
+ *
+ */
+
+#include "emu.h"
+#include "bt450.h"
+
+#define LOG_READS   (1U << 1)
+#define LOG_WRITES  (1U << 2)
+
+#define VERBOSE (LOG_WRITES)
+
+#include "logmacro.h"
+
+DEFINE_DEVICE_TYPE(BT450, bt450_device, "bt450", "Brooktree Bt450 16x12 Color RAMDAC")
+
+bt450_device::bt450_device(machine_config const &mconfig, char const *tag, device_t *owner, u32 clock)
+	: device_t(mconfig, BT450, tag, owner, clock)
+	, device_palette_interface(mconfig, *this)
+	, m_address(0)
+	, m_address_rgb(0)
+	, m_color_ram(nullptr)
+{
+}
+
+void bt450_device::device_start()
+{
+	m_color_ram = std::make_unique<std::array<u8, 3>[]>(palette_entries());
+
+	save_item(NAME(m_address));
+	save_item(NAME(m_address_rgb));
+
+	save_pointer(NAME(m_color_ram), palette_entries());
+}
+
+u8 bt450_device::address_r()
+{
+	LOGMASKED(LOG_READS, "address_r 0x%02x (%s)\n", m_address, machine().describe_context());
+
+	if (!machine().side_effects_disabled())
+		m_address_rgb = 0;
+
+	return m_address;
+
+}
+
+void bt450_device::address_w(u8 data)
+{
+	LOGMASKED(LOG_WRITES, "address_w 0x%02x (%s)\n", data, machine().describe_context());
+
+	m_address_rgb = 0;
+	m_address = data;
+}
+
+u8 bt450_device::palette_r(address_space &space)
+{
+	u8 const data = (m_address < palette_entries()) ? m_color_ram[m_address][m_address_rgb] : space.unmap();
+
+	LOGMASKED(LOG_READS, "palette_r 0x%02x (%s)\n", data, machine().describe_context());
+
+	if (!machine().side_effects_disabled())
+	{
+		// increment component index and address register
+		m_address_rgb = (m_address_rgb + 1) % 3;
+		if (m_address_rgb == 0)
+			m_address++;
+	}
+
+	return data;
+}
+
+void bt450_device::palette_w(u8 data)
+{
+	LOGMASKED(LOG_WRITES, "palette_w 0x%02x (%s)\n", data, machine().describe_context());
+
+	if (m_address < palette_entries())
+	{
+		m_color_ram[m_address][m_address_rgb] = data & 0x0f;
+
+		// update the mame palette to match the device
+		if (m_address_rgb == 2)
+			set_pen_color(m_address, rgb_t(
+				m_color_ram[m_address][0] << 4,
+				m_color_ram[m_address][1] << 4,
+				m_color_ram[m_address][2] << 4));
+	}
+
+	// increment component index and address register
+	m_address_rgb = (m_address_rgb + 1) % 3;
+	if (m_address_rgb == 0)
+		m_address++;
+}

src/devices/video/bt450.h

@@ -0,0 +1,37 @@
+// license:BSD-3-Clause
+// copyright-holders:Patrick Mackinlay
+
+#ifndef MAME_VIDEO_BT450_H
+#define MAME_VIDEO_BT450_H
+
+#pragma once
+
+class bt450_device
+	: public device_t
+	, public device_palette_interface
+{
+public:
+	bt450_device(machine_config const &mconfig, char const *tag, device_t *owner, u32 clock);
+
+	u8 address_r();
+	void address_w(u8 data);
+	u8 palette_r(address_space &space);
+	void palette_w(u8 data);
+
+protected:
+	// device_palette_interface implementation
+	virtual void device_start() override ATTR_COLD;
+
+	// device_palette_interface implementation
+	virtual u32 palette_entries() const noexcept override { return 16 + 3; }
+
+private:
+	u8 m_address;
+	u8 m_address_rgb;
+
+	std::unique_ptr<std::array<u8, 3>[]> m_color_ram;
+};
+
+DECLARE_DEVICE_TYPE(BT450, bt450_device)
+
+#endif // MAME_VIDEO_BT450_H