From fa39b28906e99f49eda33fe32ba7d8c68739d3dd Mon Sep 17 00:00:00 2001 From: Federico Date: Tue, 23 Jan 2024 16:11:23 +0100 Subject: netronics/exp85.cpp: implemented rom mirroring, fixed interrupt handling timing (#11884) * Fixed interrupt management (allows step execution in the monitor) Implemented the ROM mirroring switch after boot and during interrupt handling. * Removed logging, renamed and reordered member variables and functions, removed defined, introduced constexpr for constants. * Corrected typos in instructions on the top of the file. * Replaced tags by object finders. * Replaced the memory bank for a memory view for switching between RAM and ROM mirroring. --- src/mame/netronics/exp85.cpp | 202 ++++++++++++++++++++++++++++++++----------- 1 file changed, 153 insertions(+), 49 deletions(-) diff --git a/src/mame/netronics/exp85.cpp b/src/mame/netronics/exp85.cpp index 2040f5ea527..aa5cf88e022 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 +18,17 @@ 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 + .G + + 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 +36,8 @@ 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 +54,28 @@ #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); @@ -67,12 +84,6 @@ public: DECLARE_INPUT_CHANGED_MEMBER( trigger_rst75 ); private: - required_device m_maincpu; - required_device m_rs232; - required_device m_cassette; - required_device m_speaker; - required_memory_region m_rom; - virtual void machine_start() override; uint8_t i8355_a_r(); @@ -80,30 +91,57 @@ private: int sid_r(); void sod_w(int state); - /* cassette state */ - bool m_tape_control; + void status_out(u8 status); + void exp85_io(address_map &map); void exp85_mem(address_map &map); + + void to_change(int to); + + TIMER_CALLBACK_MEMBER(trap_delay); + + // Member variables + required_device m_maincpu; + required_device m_i8355; + required_device m_i8155; + required_device m_rs232; + required_device m_cassette; + required_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; + 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 +149,7 @@ 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 ) @@ -119,7 +158,6 @@ 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) @@ -201,6 +239,41 @@ 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 +288,47 @@ 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 +337,25 @@ 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 +363,23 @@ 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 -- cgit v1.2.3