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-rw-r--r--src/mame/netronics/exp85.cpp209
1 files changed, 157 insertions, 52 deletions
diff --git a/src/mame/netronics/exp85.cpp b/src/mame/netronics/exp85.cpp
index 2040f5ea527..2dfdd76a317 100644
--- a/src/mame/netronics/exp85.cpp
+++ b/src/mame/netronics/exp85.cpp
@@ -5,6 +5,8 @@
Explorer 85
12/05/2009 Skeleton driver.
+ 29/12/2023 Reworked driver to enable extended RAM memory,
+ MS BASIC and disable ROM mirror after boot/interrupt.
Setting Up
==========
@@ -16,6 +18,18 @@
Once started, press Space. The system will start up.
All input must be in upper case.
+ Microsoft Basic is executed entering the following 2 commands
+ in the monitor prompt:
+ .XS nnnn-F87F mmmm-C000 <CR>
+ .G <CR>
+
+ where nnnn is the previous value of the stack pointer, and mmmm is the
+ previous value of the program counter.
+
+ BASIC will request the amount of RAM memory available, 8192 (bytes) must
+ be entered.
+
+
****************************************************************************/
/*
@@ -23,8 +37,8 @@
TODO:
- dump of the hexadecimal keyboard monitor ROM
- - disable ROM mirror after boot
- - RAM expansions
+ - 64K RAM expansion
+ - Disk drive and CP/M OS support
*/
@@ -41,24 +55,28 @@
#include "imagedev/cassette.h"
#include "sound/spkrdev.h"
-
namespace {
-#define I8085A_TAG "u100"
-#define I8155_TAG "u106"
-#define I8355_TAG "u105"
+static constexpr int LOW_MEMORY_ROM_MIRROR_ENTRY = 0;
+static constexpr int LOW_MEMORY_RAM_ENTRY = 1;
class exp85_state : public driver_device
{
public:
exp85_state(const machine_config &mconfig, device_type type, const char *tag)
: driver_device(mconfig, type, tag)
- , m_maincpu(*this, I8085A_TAG)
+ , m_maincpu(*this, "u100")
+ , m_i8355(*this, "u105")
+ , m_i8155(*this, "u106")
, m_rs232(*this, "rs232")
, m_cassette(*this, "cassette")
, m_speaker(*this, "speaker")
- , m_rom(*this, I8085A_TAG)
+ , m_rom(*this, "u105") // the 8355 chip contains the monitor ROM
+ , m_low_memory_view(*this, "low_memory_view")
+ , m_is_preparing_interrupt_call(false)
+ , m_ignore_timer_out(true)
, m_tape_control(0)
+ , m_timer(nullptr)
{ }
void exp85(machine_config &config);
@@ -67,43 +85,64 @@ public:
DECLARE_INPUT_CHANGED_MEMBER( trigger_rst75 );
private:
- required_device<i8085a_cpu_device> m_maincpu;
- required_device<rs232_port_device> m_rs232;
- required_device<cassette_image_device> m_cassette;
- required_device<speaker_sound_device> m_speaker;
- required_memory_region m_rom;
-
- virtual void machine_start() override;
+ virtual void machine_start() override ATTR_COLD;
uint8_t i8355_a_r();
void i8355_a_w(uint8_t data);
int sid_r();
void sod_w(int state);
- /* cassette state */
+ void status_out(u8 status);
+
+ void exp85_io(address_map &map) ATTR_COLD;
+ void exp85_mem(address_map &map) ATTR_COLD;
+
+ void to_change(int to);
+
+ TIMER_CALLBACK_MEMBER(trap_delay);
+
+ // Member variables
+ required_device<i8085a_cpu_device> m_maincpu;
+ required_device<i8355_device> m_i8355;
+ required_device<i8155_device> m_i8155;
+ required_device<rs232_port_device> m_rs232;
+ required_device<cassette_image_device> m_cassette;
+ required_device<speaker_sound_device> m_speaker;
+ required_memory_region m_rom;
+ memory_view m_low_memory_view;
+
+ bool m_is_preparing_interrupt_call;
+ bool m_ignore_timer_out;
bool m_tape_control;
- void exp85_io(address_map &map);
- void exp85_mem(address_map &map);
+ emu_timer *m_timer;
};
-/* Memory Maps */
+/* Memory Maps */
void exp85_state::exp85_mem(address_map &map)
{
map.unmap_value_high();
- map(0x0000, 0x07ff).bankr("bank1");
+ // Extended RAM or mapped monitor ROM (only during interrupt and reset)
+ map(0x0000, 0x1fff).view(m_low_memory_view);
+ // Microsoft BASIC ROM
map(0xc000, 0xdfff).rom();
- map(0xf000, 0xf7ff).rom();
- map(0xf800, 0xf8ff).ram();
+ // Monitor ROM in the 8355 chip
+ map(0xf000, 0xf7ff).rom().region(m_rom, 0);
+ // 256 bytes of RAM of level A in the 8155 chip.
+ map(0xf800, 0xf8ff).rw(m_i8155, FUNC(i8155_device::memory_r), FUNC(i8155_device::memory_w));
+
+ // monitor ROM mirror
+ m_low_memory_view[LOW_MEMORY_ROM_MIRROR_ENTRY](0x0000, 0x07ff).rom().region(m_rom, 0);
+ // extended RAM
+ m_low_memory_view[LOW_MEMORY_RAM_ENTRY](0x0000, 0x1fff).ram();
}
void exp85_state::exp85_io(address_map &map)
{
map.unmap_value_high();
map.global_mask(0xff);
- map(0xf0, 0xf3).rw(I8355_TAG, FUNC(i8355_device::io_r), FUNC(i8355_device::io_w));
- map(0xf8, 0xfd).rw(I8155_TAG, FUNC(i8155_device::io_r), FUNC(i8155_device::io_w));
-// map(0xfe, 0xff).rw(I8279_TAG, FUNC(i8279_device::read), FUNC(i8279_device::write));
+ map(0xf0, 0xf3).rw(m_i8355, FUNC(i8355_device::io_r), FUNC(i8355_device::io_w));
+ map(0xf8, 0xfd).rw(m_i8155, FUNC(i8155_device::io_r), FUNC(i8155_device::io_w));
}
/* Input Ports */
@@ -111,6 +150,7 @@ void exp85_state::exp85_io(address_map &map)
INPUT_CHANGED_MEMBER( exp85_state::trigger_reset )
{
m_maincpu->set_input_line(INPUT_LINE_RESET, newval ? CLEAR_LINE : ASSERT_LINE);
+ m_low_memory_view.select(LOW_MEMORY_ROM_MIRROR_ENTRY);
}
INPUT_CHANGED_MEMBER( exp85_state::trigger_rst75 )
@@ -119,10 +159,9 @@ INPUT_CHANGED_MEMBER( exp85_state::trigger_rst75 )
}
static INPUT_PORTS_START( exp85 )
-
PORT_START("SPECIAL")
- PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_KEYPAD ) PORT_NAME("R") PORT_CODE(KEYCODE_F1) PORT_CHANGED_MEMBER(DEVICE_SELF, exp85_state, trigger_reset, 0)
- PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_KEYPAD ) PORT_NAME("I") PORT_CODE(KEYCODE_F2) PORT_CHANGED_MEMBER(DEVICE_SELF, exp85_state, trigger_rst75, 0)
+ PORT_BIT( 0x01, IP_ACTIVE_LOW, IPT_KEYPAD ) PORT_NAME("R") PORT_CODE(KEYCODE_F1) PORT_CHANGED_MEMBER(DEVICE_SELF, FUNC(exp85_state::trigger_reset), 0)
+ PORT_BIT( 0x02, IP_ACTIVE_LOW, IPT_KEYPAD ) PORT_NAME("I") PORT_CODE(KEYCODE_F2) PORT_CHANGED_MEMBER(DEVICE_SELF, FUNC(exp85_state::trigger_rst75), 0)
INPUT_PORTS_END
/* 8355 Interface */
@@ -201,6 +240,41 @@ void exp85_state::sod_w(int state)
}
}
+/* Memory mapping mgmt during reset and interrupt */
+
+void exp85_state::status_out(u8 status)
+{
+ // In the real hardware this is monitored via the IO/M, S0, S1
+ // and ALE output pins of the 8085.
+ // Since these pins are not emulated, then we must explicitly get the internal
+ // interrupt acknowledge state (0x23 or 0x26) and behave as the monitor expects.
+ auto current_pc = m_maincpu->pc();
+ if (status == 0x23 || status == 0x26)
+ {
+ // When an interrupt is triggered the low memory shall be set to the ROM mirror
+ m_is_preparing_interrupt_call = true;
+ m_low_memory_view.select(LOW_MEMORY_ROM_MIRROR_ENTRY);
+ }
+ else if (m_is_preparing_interrupt_call && (current_pc & 0xff00) == 0x0000)
+ {
+ // Avoids setting the lower memory back to RAM until
+ // it branches to the interrupt handler.
+ m_is_preparing_interrupt_call = false;
+ }
+ else if (!m_is_preparing_interrupt_call && (current_pc & 0xf000) == 0xf000)
+ {
+ // When the interrupt handler is executing and the address is >= 0xf000
+ // the low memory is mapped to RAM
+ m_low_memory_view.select(LOW_MEMORY_RAM_ENTRY);
+ }
+
+}
+
+//**************************************************************************
+// INPUT PORTS
+//**************************************************************************
+
+
/* Terminal Interface */
static DEVICE_INPUT_DEFAULTS_START( terminal )
@@ -215,16 +289,47 @@ DEVICE_INPUT_DEFAULTS_END
void exp85_state::machine_start()
{
- /* setup memory banking */
- membank("bank1")->configure_entry(0, m_rom->base() + 0xf000);
- membank("bank1")->configure_entry(1, m_rom->base());
- membank("bank1")->set_entry(0);
+ /* clear the trap line that is asserted on start */
+ m_maincpu->set_input_line(I8085_TRAP_LINE, CLEAR_LINE);
+
+ /* setup memory mirror switch */
+ m_low_memory_view.select(LOW_MEMORY_ROM_MIRROR_ENTRY);
save_item(NAME(m_tape_control));
+
+ m_timer = timer_alloc(FUNC(exp85_state::trap_delay), this);
}
-/* Machine Driver */
+void exp85_state::to_change(int to)
+{
+ // In the 8155 implementation the TIMER-OUT line (to) is
+ // asserted by default on initialization; this generates a spurious exception
+ // avoided here via an ignore flag.
+ if (m_ignore_timer_out)
+ {
+ m_ignore_timer_out = false;
+ return;
+ }
+ // The 8155 has a max TIMER-IN to TIMER-OUT delay of 400ns (datasheet page 3-256). In a real system
+ // this delay was measured in ~70ns. This is enough for the next instruction cycle to start
+ // and for the interrupt to be acknowledged one instruction later. This effect is fundamental
+ // for the ROM monitor stepping functionality, since it depends heavily on interrupting when the
+ // next instruction of the user program is being executed.
+ // MAME allows to set a timer of 70ns but that is not enough to get the CPU scheduled for at least 1 cycle
+ // before the interrupt is serviced, so we program a timer to expire beyond a full clock cycle.
+ m_timer->adjust(m_i8155->clocks_to_attotime(2), to);
+}
+
+TIMER_CALLBACK_MEMBER(exp85_state::trap_delay)
+{
+ // The 8155 TIMER-OUT line is connected to the TRAP input line of the 8085;
+ // that line is set from the start high, and since there is no change in that line, the
+ // interrup is never requested (datasheet, page 6-13).
+ m_maincpu->set_input_line(I8085_TRAP_LINE, param == 1 ? ASSERT_LINE : CLEAR_LINE);
+}
+
+/* Machine Driver */
void exp85_state::exp85(machine_config &config)
{
/* basic machine hardware */
@@ -233,17 +338,25 @@ void exp85_state::exp85(machine_config &config)
m_maincpu->set_addrmap(AS_IO, &exp85_state::exp85_io);
m_maincpu->in_sid_func().set(FUNC(exp85_state::sid_r));
m_maincpu->out_sod_func().set(FUNC(exp85_state::sod_w));
+ m_maincpu->out_status_func().set(FUNC(exp85_state::status_out));
/* sound hardware */
SPEAKER(config, "mono").front_center();
SPEAKER_SOUND(config, m_speaker).add_route(ALL_OUTPUTS, "mono", 0.25);
/* devices */
- I8155(config, I8155_TAG, 6.144_MHz_XTAL/2);
- i8355_device &i8355(I8355(config, I8355_TAG, 6.144_MHz_XTAL/2));
- i8355.in_pa().set(FUNC(exp85_state::i8355_a_r));
- i8355.out_pa().set(FUNC(exp85_state::i8355_a_w));
+ // The Explorer-85 uses a 6.144MHz clock, but the Intel 8085 divides by 2 this
+ // input frequency to give the processor internal operating frequency.
+ // The bus is connected to the CLK (out) of the 8085, running also
+ // at 6.144MHz divided by 2.
+ I8155(config, m_i8155, 6.144_MHz_XTAL/2);
+ m_i8155->out_to_callback().set(FUNC(exp85_state::to_change));
+
+
+ I8355(config, m_i8355, 6.144_MHz_XTAL/2);
+ m_i8355->in_pa().set(FUNC(exp85_state::i8355_a_r));
+ m_i8355->out_pa().set(FUNC(exp85_state::i8355_a_w));
CASSETTE(config, m_cassette);
m_cassette->set_default_state(CASSETTE_STOPPED | CASSETTE_MOTOR_ENABLED | CASSETTE_SPEAKER_ENABLED);
@@ -251,31 +364,23 @@ void exp85_state::exp85(machine_config &config)
RS232_PORT(config, "rs232", default_rs232_devices, "terminal").set_option_device_input_defaults("terminal", DEVICE_INPUT_DEFAULTS_NAME(terminal));
- /* internal ram */
- RAM(config, RAM_TAG).set_default_size("256").set_extra_options("4K");
}
/* ROMs */
ROM_START( exp85 )
- ROM_REGION( 0x10000, I8085A_TAG, 0 )
+ ROM_REGION( 0x10000, "u100", 0 ) // Microsoft BASIC
ROM_DEFAULT_BIOS("eia")
ROM_LOAD( "c000.bin", 0xc000, 0x0800, CRC(73ce4aad) SHA1(2c69cd0b6c4bdc92f4640bce18467e4e99255bab) )
ROM_LOAD( "c800.bin", 0xc800, 0x0800, CRC(eb3fdedc) SHA1(af92d07f7cb7533841b16e1176401363176857e1) )
ROM_LOAD( "d000.bin", 0xd000, 0x0800, CRC(c10c4a22) SHA1(30588ba0b27a775d85f8c581ad54400c8521225d) )
ROM_LOAD( "d800.bin", 0xd800, 0x0800, CRC(dfa43ef4) SHA1(56a7e7a64928bdd1d5f0519023d1594cacef49b3) )
- ROM_SYSTEM_BIOS( 0, "eia", "EIA Terminal" )
- ROMX_LOAD( "ex 85.u105", 0xf000, 0x0800, CRC(1a99d0d9) SHA1(57b6d48e71257bc4ef2d3dddc9b30edf6c1db766), ROM_BIOS(0) )
- ROM_SYSTEM_BIOS( 1, "hex", "Hex Keyboard" )
- ROMX_LOAD( "1kbd.u105", 0xf000, 0x0800, NO_DUMP, ROM_BIOS(1) )
-
- ROM_REGION( 0x800, I8355_TAG, ROMREGION_ERASE00 )
-
-/* ROM_DEFAULT_BIOS("terminal")
- ROM_SYSTEM_BIOS( 0, "terminal", "Terminal" )
- ROMX_LOAD( "eia.u105", 0xf000, 0x0800, CRC(1a99d0d9) SHA1(57b6d48e71257bc4ef2d3dddc9b30edf6c1db766), ROM_BIOS(0) )
- ROM_SYSTEM_BIOS( 1, "hexkbd", "Hex Keyboard" )
- ROMX_LOAD( "hex.u105", 0xf000, 0x0800, NO_DUMP, ROM_BIOS(1) )*/
+
+ ROM_REGION( 0x800, "u105", 0 ) // Explorer 85 Monitor
+ ROM_SYSTEM_BIOS( 0, "eia", "EIA Terminal" ) // Serial terminal ROM
+ ROMX_LOAD( "ex 85.u105", 0x0000, 0x0800, CRC(1a99d0d9) SHA1(57b6d48e71257bc4ef2d3dddc9b30edf6c1db766), ROM_BIOS(0) )
+ ROM_SYSTEM_BIOS( 1, "hex", "Hex Keyboard" ) // Keypad ROM (not available)
+ ROMX_LOAD( "1kbd.u105", 0x0000, 0x0800, NO_DUMP, ROM_BIOS(1) )
ROM_END
} // anonymous namespace