Add a device as proof of concept which merges several input lines into a common output line, supporting both active high and active low inputs

scripts/src/machine.lua

@@ -2914,3 +2914,14 @@ if (MACHINES["SCNXX562"]~=null) then
 		MAME_DIR .. "src/devices/machine/scnxx562.h",
 	}
 end
+
+---------------------------------------------------
+--
+--@src/devices/machine/input_merger.h,MACHINES["INPUT_MERGER"] = true
+---------------------------------------------------
+if (MACHINES["INPUT_MERGER"]~=null) then
+	files {
+		MAME_DIR .. "src/devices/machine/input_merger.cpp",
+		MAME_DIR .. "src/devices/machine/input_merger.h",
+	}
+end

scripts/target/mame/arcade.lua

@@ -572,6 +572,7 @@ MACHINES["PCI9050"] = true
 MACHINES["GENPC"] = true
 MACHINES["GEN_LATCH"] = true
 MACHINES["WATCHDOG"] = true
+MACHINES["INPUT_MERGER"] = true
 
 --------------------------------------------------
 -- specify available bus cores

scripts/target/mame/mess.lua

@@ -586,6 +586,7 @@ MACHINES["APPLE_FDC"] = true
 MACHINES["SONY_DRIVE"] = true
 MACHINES["SCNXX562"] = true
 MACHINES["FGA002"] = true
+MACHINES["INPUT_MERGER"] = true
 
 --------------------------------------------------
 -- specify available bus cores

src/devices/machine/input_merger.cpp

@@ -0,0 +1,122 @@
+// license:GPL-2.0+
+// copyright-holders:Dirk Best
+/***************************************************************************
+
+    Input Merger
+
+    Used to connect multiple lines to a single device input while
+    keeping it pulled high or low
+
+***************************************************************************/
+
+#include "input_merger.h"
+
+#include <algorithm>
+#include <iterator>
+
+
+//**************************************************************************
+//  DEVICE DEFINITIONS
+//**************************************************************************
+
+const device_type INPUT_MERGER_ACTIVE_HIGH = &device_creator<input_merger_active_high_device>;
+const device_type INPUT_MERGER_ACTIVE_LOW = &device_creator<input_merger_active_low_device>;
+
+
+//**************************************************************************
+//  INPUT ADAPTER
+//**************************************************************************
+
+//-------------------------------------------------
+//  input_merger_device - constructor
+//-------------------------------------------------
+
+input_merger_device::input_merger_device(machine_config const &mconfig, device_type type,
+	char const *name, char const *tag, device_t *owner, UINT32 clock, char const *shortname, char const *source)
+	: device_t(mconfig, type, name, tag, owner, clock, shortname, source),
+	m_output_handler(*this)
+{
+}
+
+//-------------------------------------------------
+//  input_merger_device - destructor
+//-------------------------------------------------
+
+input_merger_device::~input_merger_device()
+{
+}
+
+//-------------------------------------------------
+//  device_start - device-specific startup
+//-------------------------------------------------
+
+void input_merger_device::device_start()
+{
+	m_output_handler.resolve_safe();
+}
+
+
+//**************************************************************************
+//  INPUT ADAPTER ACTIVE HIGH
+//**************************************************************************
+
+//-------------------------------------------------
+//  input_merger_active_high_device - constructor
+//-------------------------------------------------
+
+input_merger_active_high_device::input_merger_active_high_device(machine_config const &mconfig, char const *tag, device_t *owner,	UINT32 clock)
+	: input_merger_device(mconfig,	INPUT_MERGER_ACTIVE_HIGH, "Input Merger (Active High)", tag, owner, clock, "input_merger_hi", __FILE__)
+{
+}
+
+//-------------------------------------------------
+//  device_reset - device-specific reset
+//-------------------------------------------------
+
+void input_merger_active_high_device::device_reset()
+{
+	std::fill(std::begin(m_state), std::end(m_state), false);
+}
+
+//-------------------------------------------------
+//  update_state - verify current input line state
+//-------------------------------------------------
+
+void input_merger_active_high_device::update_state()
+{
+	bool state = std::any_of(std::begin(m_state), std::end(m_state), [&](bool state) { return state == true; });
+	m_output_handler(state ? ASSERT_LINE : CLEAR_LINE);
+}
+
+
+//**************************************************************************
+//  INPUT ADAPTER ACTIVE LOW
+//**************************************************************************
+
+//-------------------------------------------------
+//  input_merger_active_low_device - constructor
+//-------------------------------------------------
+
+input_merger_active_low_device::input_merger_active_low_device(machine_config const &mconfig, char const *tag, device_t *owner,	UINT32 clock)
+	: input_merger_device(mconfig,	INPUT_MERGER_ACTIVE_LOW, "Input Merger (Active Low)", tag, owner, clock, "input_merger_lo", __FILE__)
+{
+}
+
+//-------------------------------------------------
+//  device_reset - device-specific reset
+//-------------------------------------------------
+
+void input_merger_active_low_device::device_reset()
+{
+	std::fill(std::begin(m_state), std::end(m_state), true);
+}
+
+//-------------------------------------------------
+//  update_state - verify current input line state
+//-------------------------------------------------
+
+void input_merger_active_low_device::update_state()
+{
+	bool state = std::any_of(std::begin(m_state), std::end(m_state), [&](bool state) { return state == false; });
+	m_output_handler(state ? ASSERT_LINE : CLEAR_LINE);
+}

src/devices/machine/input_merger.h

@@ -0,0 +1,107 @@
+// license:GPL-2.0+
+// copyright-holders:Dirk Best
+/***************************************************************************
+
+	Input Merger
+
+    Used to connect multiple lines to a single device input while
+    keeping it pulled high or low
+
+***************************************************************************/
+
+#pragma once
+
+#ifndef __INPUT_MERGER_H__
+#define __INPUT_MERGER_H__
+
+#include "emu.h"
+
+
+//**************************************************************************
+//  INTERFACE CONFIGURATION MACROS
+//**************************************************************************
+
+#define MCFG_INPUT_MERGER_ACTIVE_HIGH(_tag) \
+	MCFG_DEVICE_ADD(_tag, INPUT_MERGER_ACTIVE_HIGH, 0)
+
+#define MCFG_INPUT_MERGER_ACTIVE_LOW(_tag) \
+	MCFG_DEVICE_ADD(_tag, INPUT_MERGER_ACTIVE_LOW, 0)
+
+#define MCFG_INPUT_MERGER_OUTPUT_HANDLER(_devcb) \
+	devcb = &input_merger_device::set_output_handler(*device, DEVCB_##_devcb);
+
+
+//**************************************************************************
+//  TYPE DEFINITIONS
+//**************************************************************************
+
+// ======================> input_merger_device
+
+class input_merger_device : public device_t
+{
+public:
+	// callback
+	template<class _Object> static devcb_base &set_output_handler(device_t &device, _Object object)
+		{ return downcast<input_merger_device &>(device).m_output_handler.set_callback(object); }
+
+	// input lines
+	DECLARE_WRITE_LINE_MEMBER( in0_w ) { m_state[0] = state; update_state(); };
+	DECLARE_WRITE_LINE_MEMBER( in1_w ) { m_state[1] = state; update_state(); };
+	DECLARE_WRITE_LINE_MEMBER( in2_w ) { m_state[2] = state; update_state(); };
+	DECLARE_WRITE_LINE_MEMBER( in3_w ) { m_state[3] = state; update_state(); };
+	DECLARE_WRITE_LINE_MEMBER( in4_w ) { m_state[4] = state; update_state(); };
+	DECLARE_WRITE_LINE_MEMBER( in5_w ) { m_state[5] = state; update_state(); };
+	DECLARE_WRITE_LINE_MEMBER( in6_w ) { m_state[6] = state; update_state(); };
+	DECLARE_WRITE_LINE_MEMBER( in7_w ) { m_state[7] = state; update_state(); };
+
+protected:
+	// constructor/destructor
+	input_merger_device(machine_config const &mconfig, device_type type, char const *name, char const *tag, device_t *owner, UINT32 clock, char const *shortname, char const *source);
+	virtual ~input_merger_device() override;
+
+	// device-level overrides
+	virtual void device_start() override;
+
+	virtual void update_state() = 0;
+
+	devcb_write_line m_output_handler;
+	bool m_state[8];
+};
+
+// ======================> input_merger_active_high_device
+
+class input_merger_active_high_device : public input_merger_device
+{
+public:
+	input_merger_active_high_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock);
+
+protected:
+	// device-level overrides
+	virtual void device_reset() override;
+
+	// input_merger device overrides
+	virtual void update_state() override;
+};
+
+// ======================> input_merger_active_low_device
+
+class input_merger_active_low_device : public input_merger_device
+{
+public:
+	input_merger_active_low_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock);
+
+protected:
+	// device-level overrides
+	virtual void device_reset() override;
+
+	// input_merger device overrides
+	virtual void update_state() override;
+};
+
+
+// device type definition
+extern const device_type INPUT_MERGER_ACTIVE_HIGH;
+extern const device_type INPUT_MERGER_ACTIVE_LOW;
+
+
+#endif  /* __INPUT_MERGER_H__ */