bus/rs232: Preliminary emulation of the Mockingboard D "sound card" for the Apple IIc. [R. Belmont, Apple II Documentation Project]

scripts/src/bus.lua

@@ -2656,6 +2656,8 @@ if (BUSES["RS232"]~=null) then
 		MAME_DIR .. "src/devices/bus/rs232/exorterm.h",
 		MAME_DIR .. "src/devices/bus/rs232/rs232_sync_io.cpp",
 		MAME_DIR .. "src/devices/bus/rs232/rs232_sync_io.h",
+		MAME_DIR .. "src/devices/bus/rs232/mboardd.cpp",
+		MAME_DIR .. "src/devices/bus/rs232/mboardd.h",
 	}
 end
 

src/devices/bus/rs232/mboardd.cpp

@@ -0,0 +1,105 @@
+// license:BSD-3-Clause
+// copyright-holders:R. Belmont
+
+/*
+	mboardd.cpp - Mockingboard D emulation
+	by R. Belmont
+
+	The Apple IIc didn't have slots, so Sweet Micro Systems came up with this, a Mockingboard
+	in a little box that attached to the IIc's modem port.  There's nothing special about the
+	IIc though - with a proper cable, anything that speaks 9600 8N1 RS-232 could drive this
+	device.
+
+	A decent disassembly of the 6803 firmware is available from the Apple II Documentation Project:
+	https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Audio/Sweet%20Microsystems%20Mockingboard/Source%20Code/
+
+*/
+
+#include "emu.h"
+#include "mboardd.h"
+#include "speaker.h"
+
+ROM_START(mboardd)
+	ROM_REGION(0x800, "mbcpu", 0)
+	ROM_LOAD("mockingboard d rom.bin", 0x000000, 0x000800, CRC(277b1813) SHA1(e8d20f4b59fe867ff76434d35a14d2cbdc8533e3))
+ROM_END
+
+mockingboard_d_device::mockingboard_d_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
+	: device_t(mconfig, SERIAL_MOCKINGBOARD_D, tag, owner, clock)
+	, device_rs232_port_interface(mconfig, *this)
+	, m_cpu(*this, "mbdcpu")
+	, m_ay1(*this, "ay1")
+	, m_ay2(*this, "ay2")
+{
+}
+
+void mockingboard_d_device::device_add_mconfig(machine_config &config)
+{
+	M6803(config, m_cpu, 4.9152_MHz_XTAL);	// value reverse-engineered from 9600 baud SCI rate needed
+	m_cpu->set_addrmap(AS_PROGRAM, &mockingboard_d_device::m6803_mem);
+	m_cpu->in_p2_cb().set(FUNC(mockingboard_d_device::p2_r));
+	m_cpu->out_p1_cb().set(FUNC(mockingboard_d_device::p1_w));
+	m_cpu->out_ser_tx_cb().set(FUNC(mockingboard_d_device::ser_tx_w));
+
+	SPEAKER(config, "lspeaker").front_left();
+	SPEAKER(config, "rspeaker").front_right();
+	AY8913(config, m_ay1, 1022727);
+	m_ay1->add_route(ALL_OUTPUTS, "lspeaker", 0.5);
+	AY8913(config, m_ay2, 1022727);
+	m_ay2->add_route(ALL_OUTPUTS, "lspeaker", 0.5);
+}
+
+const tiny_rom_entry *mockingboard_d_device::device_rom_region() const
+{
+	return ROM_NAME(mboardd);
+}
+
+void mockingboard_d_device::device_start()
+{
+}
+
+void mockingboard_d_device::device_reset()
+{
+	output_dcd(0);
+	output_dsr(0);
+	output_cts(0);
+}
+
+void mockingboard_d_device::m6803_mem(address_map &map)
+{
+	map(0x8000, 0x83ff).ram();
+	// SSI-263 at a000/a001
+	map(0xc000, 0xc000).w(FUNC(mockingboard_d_device::c000_w));
+	map(0xf800, 0xffff).rom().region("mbcpu", 0);
+}
+
+WRITE_LINE_MEMBER(mockingboard_d_device::input_txd)
+{
+	m_rx_state = (state & 1);
+}
+
+void mockingboard_d_device::p1_w(u8 data)
+{
+	if (BIT(data, 3))
+	{
+		m_ay2->address_w(m_c000_latch);
+		//printf("%02x to AY2 address\n", m_c000_latch);
+	}
+	else if (BIT(data, 2))
+	{
+		m_ay2->data_w(m_c000_latch);
+		//printf("%02x to AY2 data\n", m_c000_latch);
+	}
+	else if (BIT(data, 1))
+	{
+		m_ay1->address_w(m_c000_latch);
+		//printf("%02x to AY1 address\n", m_c000_latch);
+	}
+	else if (BIT(data, 0))
+	{
+		m_ay1->data_w(m_c000_latch);
+		//printf("%02x to AY1 data\n", m_c000_latch);
+	}
+}
+
+DEFINE_DEVICE_TYPE(SERIAL_MOCKINGBOARD_D, mockingboard_d_device, "mockingboardd", "Sweet Micro Systems Mockingboard D")

src/devices/bus/rs232/mboardd.h

@@ -0,0 +1,45 @@
+// license:BSD-3-Clause
+// copyright-holders:R. Belmont
+
+#ifndef MAME_BUS_RS232_MBOARDD_H
+#define MAME_BUS_RS232_MBOARDD_H
+
+#pragma once
+
+#include "rs232.h"
+#include "cpu/m6800/m6801.h"
+#include "sound/ay8910.h"
+
+class mockingboard_d_device : public device_t, public device_rs232_port_interface
+{
+public:
+	mockingboard_d_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
+
+	virtual DECLARE_WRITE_LINE_MEMBER( input_txd ) override;
+
+	required_device<m6803_cpu_device> m_cpu;
+	required_device<ay8913_device> m_ay1;
+	required_device<ay8913_device> m_ay2;
+
+protected:
+	virtual void device_start() override;
+	virtual void device_reset() override;
+	virtual void device_add_mconfig(machine_config &config) override;
+	virtual const tiny_rom_entry *device_rom_region() const override;
+
+private:
+	u8 p2_r() { return m_rx_state<<3; };
+	void p1_w(u8 data);
+
+	void ser_tx_w(int state) { output_rxd(state); }
+
+	void c000_w(u8 data) { m_c000_latch = data; };
+
+	void m6803_mem(address_map &map);
+	int m_rx_state;
+	u8 m_c000_latch;
+};
+
+DECLARE_DEVICE_TYPE(SERIAL_MOCKINGBOARD_D, mockingboard_d_device)
+
+#endif // MAME_BUS_RS232_MBOARDD_H

src/devices/bus/rs232/rs232.cpp

@@ -172,6 +172,7 @@ device_rs232_port_interface::~device_rs232_port_interface()
 #include "terminal.h"
 #include "ie15.h"
 #include "rs232_sync_io.h"
+#include "mboardd.h"
 
 void default_rs232_devices(device_slot_interface &device)
 {
@@ -187,4 +188,5 @@ void default_rs232_devices(device_slot_interface &device)
 	device.option_add("sunkbd", SUN_KBD_ADAPTOR);
 	device.option_add("swtpc8212", SERIAL_TERMINAL_SWTPC8212);
 	device.option_add("terminal", SERIAL_TERMINAL);
+	device.option_add("mockingboard", SERIAL_MOCKINGBOARD_D);
 }