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+/*********************************************************************
+
+ a2themill.c
+
+ Implementation of the Stellation Two The Mill 6809 card
+
+ The OS9 add-on changes the address mapping as follows:
+ 6809 0x0000-0xafff -> 6502 0x1000-0xbfff
+ 6809 0xb000-0xdfff -> 6502 0xd000-0xffff
+ 6809 0xe000-0xefff -> 6502 0xc000-0xcfff
+ 6809 0xf000-0xffff -> 6502 0x0000-0x0fff
+
+ (reference: http://mirrors.apple2.org.za/ground.icaen.uiowa.edu/MiscInfo/Hardware/mill.6809 )
+
+ ProDOS "Stellation The Mill Disk.po" requires Mill in slot 2; boot
+ the disc and type "-DEMO1" and press Enter to launch the simple demo.
+
+ The OS9 disk image available around the internet seems to be bad - the
+ 6809 boot vector is 0x4144 which maps to 6502 0x5144 and there's all
+ zeros from 6502 1000-8fff. There is valid 6809 code from 9000-BFFF
+ at the point where it wants to boot the 6809, but I don't know what
+ is supposed to be the entry point.
+
+*********************************************************************/
+
+#include "a2themill.h"
+#include "includes/apple2.h"
+#include "cpu/m6809/m6809.h"
+
+/***************************************************************************
+ PARAMETERS
+***************************************************************************/
+
+#define MILL_VERBOSE (0)
+
+//**************************************************************************
+// GLOBAL VARIABLES
+//**************************************************************************
+
+const device_type A2BUS_THEMILL = &device_creator<a2bus_themill_device>;
+
+#define M6809_TAG "m6809"
+
+static ADDRESS_MAP_START( m6809_mem, AS_PROGRAM, 8, a2bus_themill_device )
+ AM_RANGE(0x0000, 0xffff) AM_READWRITE(dma_r, dma_w)
+ADDRESS_MAP_END
+
+MACHINE_CONFIG_FRAGMENT( a2themill )
+ MCFG_CPU_ADD(M6809_TAG, M6809, 1021800) // M6809 runs at ~1 MHz as per Stellation Two's print ads
+ MCFG_CPU_PROGRAM_MAP(m6809_mem)
+MACHINE_CONFIG_END
+
+/***************************************************************************
+ FUNCTION PROTOTYPES
+***************************************************************************/
+
+//-------------------------------------------------
+// machine_config_additions - device-specific
+// machine configurations
+//-------------------------------------------------
+
+machine_config_constructor a2bus_themill_device::device_mconfig_additions() const
+{
+ return MACHINE_CONFIG_NAME( a2themill );
+}
+
+//**************************************************************************
+// LIVE DEVICE
+//**************************************************************************
+
+a2bus_themill_device::a2bus_themill_device(const machine_config &mconfig, device_type type, const char *name, const char *tag, device_t *owner, UINT32 clock) :
+ device_t(mconfig, type, name, tag, owner, clock),
+ device_a2bus_card_interface(mconfig, *this),
+ m_6809(*this, M6809_TAG),
+ m_6502space(NULL)
+{
+ m_shortname = "a2themill";
+}
+
+a2bus_themill_device::a2bus_themill_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock) :
+ device_t(mconfig, A2BUS_THEMILL, "Stellation Two The Mill", tag, owner, clock),
+ device_a2bus_card_interface(mconfig, *this),
+ m_6809(*this, M6809_TAG),
+ m_6502space(NULL)
+{
+ m_shortname = "a2themill";
+}
+
+//-------------------------------------------------
+// device_start - device-specific startup
+//-------------------------------------------------
+
+void a2bus_themill_device::device_start()
+{
+ // set_a2bus_device makes m_slot valid
+ set_a2bus_device();
+
+ save_item(NAME(m_bEnabled));
+ save_item(NAME(m_flipAddrSpace));
+ save_item(NAME(m_6809Mode));
+ save_item(NAME(m_status));
+}
+
+void a2bus_themill_device::device_reset()
+{
+ m_bEnabled = false;
+ m_6502space = NULL;
+ m_flipAddrSpace = false;
+ m_6809Mode = false;
+ m_status = 0xc0; // OS9 loader relies on this
+ device_set_input_line(m_6809, INPUT_LINE_HALT, ASSERT_LINE);
+ device_set_input_line(m_6809, INPUT_LINE_RESET, ASSERT_LINE);
+}
+
+UINT8 a2bus_themill_device::read_c0nx(address_space &space, UINT8 offset)
+{
+ return m_status;
+}
+
+void a2bus_themill_device::write_c0nx(address_space &space, UINT8 offset, UINT8 data)
+{
+ switch (offset)
+ {
+ case 0: // 6502 IRQ
+ if (data & 0x80)
+ {
+ m_status |= 0x01;
+ lower_slot_irq();
+ }
+ else
+ {
+ m_status &= ~0x01;
+ raise_slot_irq();
+ }
+ break;
+
+ case 2: // 6809 reset
+ if (data & 0x80)
+ {
+ // steal the 6502's address space
+ m_6502space = &space;
+ m_6809->reset();
+
+ device_set_input_line(m_6809, INPUT_LINE_HALT, CLEAR_LINE);
+ device_set_input_line(m_6809, INPUT_LINE_RESET, CLEAR_LINE);
+
+ m_bEnabled = true;
+ m_status &= ~0x04;
+ }
+ else
+ {
+ device_set_input_line(m_6809, INPUT_LINE_HALT, ASSERT_LINE);
+ m_bEnabled = false;
+ m_status |= 0x04;
+ }
+ break;
+
+ case 1: // 6809 halt
+ if (data & 0x80) // release reset
+ {
+ m_status |= 0x02;
+ }
+ else
+ {
+ m_6809->reset();
+ m_status &= ~0x02;
+ }
+ break;
+
+ case 3: // 6809 NMI
+ if (data & 0x80)
+ {
+ device_set_input_line(m_6809, INPUT_LINE_NMI, CLEAR_LINE);
+ m_status |= 0x08;
+ }
+ else
+ {
+ device_set_input_line(m_6809, INPUT_LINE_NMI, ASSERT_LINE);
+ m_status &= ~0x08;
+ }
+ break;
+
+ case 4: // 6809 FIRQ
+ if (data & 0x80)
+ {
+ device_set_input_line(m_6809, M6809_FIRQ_LINE, CLEAR_LINE);
+ m_status |= 0x10;
+ }
+ else
+ {
+ device_set_input_line(m_6809, M6809_FIRQ_LINE, ASSERT_LINE);
+ m_status &= ~0x10;
+ }
+ break;
+
+ case 5: // 6809 IRQ
+ if (data & 0x80)
+ {
+ device_set_input_line(m_6809, M6809_IRQ_LINE, CLEAR_LINE);
+ m_status |= 0x20;
+ }
+ else
+ {
+ device_set_input_line(m_6809, M6809_IRQ_LINE, ASSERT_LINE);
+ m_status &= ~0x20;
+ }
+ break;
+
+ case 6:
+ if (data & 0x80) // enable ROM socket
+ {
+ m_status |= 0x40;
+ printf("The Mill: on-board ROM socket enabled; because none of these ROMs are dumped, the 6809 will not run!\n");
+ }
+ else
+ {
+ m_status &= ~0x40;
+ }
+ break;
+
+ case 7: // 6809 mapping
+ if (data & 0x80)
+ {
+ m_status |= 0x80;
+ m_flipAddrSpace = false;
+ }
+ else
+ {
+ m_status &= ~0x80;
+ m_flipAddrSpace = true;
+ }
+ break;
+
+ case 0xa: // addresses >= 0x8 are direct status writes? "Excel Flex 9" disc seems to indicate so.
+ m_status = data;
+ break;
+
+ default:
+ printf("The Mill: %02x to unhandled c0n%x\n", data, offset);
+ break;
+ }
+}
+
+READ8_MEMBER( a2bus_themill_device::dma_r )
+{
+ if (m_6502space)
+ {
+ if (m_6809Mode)
+ {
+ if (offset <= 0xafff)
+ {
+ return m_6502space->read_byte(offset+0x1000);
+ }
+ else if (offset <= 0xbfff)
+ {
+ return m_6502space->read_byte((offset&0xfff) + 0xd000);
+ }
+ else if (offset <= 0xcfff)
+ {
+ return m_6502space->read_byte((offset&0xfff) + 0xe000);
+ }
+ else if (offset <= 0xdfff)
+ {
+ return m_6502space->read_byte((offset&0xfff) + 0xf000);
+ }
+ else if (offset <= 0xefff)
+ {
+ return m_6502space->read_byte((offset&0xfff) + 0xc000);
+ }
+ else // 6809 Fxxx -> 6502 ZP
+ {
+ return m_6502space->read_byte(offset&0xfff);
+ }
+ }
+ else
+ {
+ if (m_flipAddrSpace)
+ {
+ return m_6502space->read_byte(offset^0x8000);
+ }
+ else
+ {
+ return m_6502space->read_byte(offset);
+ }
+ }
+ }
+
+ return 0xff;
+}
+
+
+//-------------------------------------------------
+// dma_w -
+//-------------------------------------------------
+
+WRITE8_MEMBER( a2bus_themill_device::dma_w )
+{
+ if (m_6502space)
+ {
+ if (m_6809Mode)
+ {
+ if (offset <= 0xafff)
+ {
+ m_6502space->write_byte(offset+0x1000, data);
+ }
+ else if (offset <= 0xbfff)
+ {
+ m_6502space->write_byte((offset&0xfff) + 0xd000, data);
+ }
+ else if (offset <= 0xcfff)
+ {
+ m_6502space->write_byte((offset&0xfff) + 0xe000, data);
+ }
+ else if (offset <= 0xdfff)
+ {
+ m_6502space->write_byte((offset&0xfff) + 0xf000, data);
+ }
+ else if (offset <= 0xefff)
+ {
+ m_6502space->write_byte((offset&0xfff) + 0xc000, data);
+ }
+ else // 6809 Fxxx -> 6502 ZP
+ {
+ m_6502space->write_byte(offset&0xfff, data);
+ }
+ }
+ else
+ {
+ if (m_flipAddrSpace)
+ {
+ m_6502space->write_byte(offset^0x8000, data);
+ }
+ else
+ {
+ m_6502space->write_byte(offset, data);
+ }
+ }
+ }
+}
+
+bool a2bus_themill_device::take_c800()
+{
+ return false;
+}
+