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https://github.com/holub/mame
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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.
This commit is contained in:
Federico
GitHub
parent
f26416a473
commit
fa39b28906
@ -5,6 +5,8 @@
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Explorer 85
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12/05/2009 Skeleton driver.
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29/12/2023 Reworked driver to enable extended RAM memory,
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MS BASIC and disable ROM mirror after boot/interrupt.
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Setting Up
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==========
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@ -16,6 +18,17 @@
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Once started, press Space. The system will start up.
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All input must be in upper case.
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Microsoft Basic is executed entering the following 2 commands
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in the monitor prompt:
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.XS nnnn-F87F mmmm-C000 <CR>
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.G <CR>
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where nnnn is the previous value of the stack pointer, and mmmm is the previous
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value of the program counter.
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Basic will request the amount of RAM memory available, 8192 (bytes) must be entered.
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****************************************************************************/
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/*
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@ -23,8 +36,8 @@
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TODO:
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- dump of the hexadecimal keyboard monitor ROM
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- disable ROM mirror after boot
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- RAM expansions
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- 64K RAM expansion
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- Disk drive and CP/M OS support
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*/
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@ -41,24 +54,28 @@
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#include "imagedev/cassette.h"
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#include "sound/spkrdev.h"
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namespace {
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#define I8085A_TAG "u100"
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#define I8155_TAG "u106"
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#define I8355_TAG "u105"
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static constexpr int LOW_MEMORY_ROM_MIRROR_ENTRY = 0;
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static constexpr int LOW_MEMORY_RAM_ENTRY = 1;
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class exp85_state : public driver_device
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{
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public:
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exp85_state(const machine_config &mconfig, device_type type, const char *tag)
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: driver_device(mconfig, type, tag)
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, m_maincpu(*this, I8085A_TAG)
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, m_maincpu(*this, "u100")
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, m_i8355(*this, "u105")
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, m_i8155(*this, "u106")
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, m_rs232(*this, "rs232")
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, m_cassette(*this, "cassette")
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, m_speaker(*this, "speaker")
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, m_rom(*this, I8085A_TAG)
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, m_rom(*this, "u105") // the 8355 chip contains the monitor ROM
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, m_low_memory_view(*this, "low_memory_view")
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, m_is_preparing_interrupt_call(false)
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, m_ignore_timer_out(true)
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, m_tape_control(0)
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, m_timer(nullptr)
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{ }
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void exp85(machine_config &config);
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@ -67,12 +84,6 @@ public:
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DECLARE_INPUT_CHANGED_MEMBER( trigger_rst75 );
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private:
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required_device<i8085a_cpu_device> m_maincpu;
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required_device<rs232_port_device> m_rs232;
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required_device<cassette_image_device> m_cassette;
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required_device<speaker_sound_device> m_speaker;
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required_memory_region m_rom;
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virtual void machine_start() override;
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uint8_t i8355_a_r();
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@ -80,30 +91,57 @@ private:
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int sid_r();
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void sod_w(int state);
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/* cassette state */
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bool m_tape_control;
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void status_out(u8 status);
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void exp85_io(address_map &map);
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void exp85_mem(address_map &map);
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void to_change(int to);
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TIMER_CALLBACK_MEMBER(trap_delay);
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// Member variables
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required_device<i8085a_cpu_device> m_maincpu;
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required_device<i8355_device> m_i8355;
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required_device<i8155_device> m_i8155;
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required_device<rs232_port_device> m_rs232;
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required_device<cassette_image_device> m_cassette;
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required_device<speaker_sound_device> m_speaker;
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required_memory_region m_rom;
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memory_view m_low_memory_view;
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bool m_is_preparing_interrupt_call;
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bool m_ignore_timer_out;
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bool m_tape_control;
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emu_timer *m_timer;
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};
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/* Memory Maps */
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/* Memory Maps */
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void exp85_state::exp85_mem(address_map &map)
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{
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map.unmap_value_high();
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map(0x0000, 0x07ff).bankr("bank1");
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// Extended RAM or mapped monitor ROM (only during interrupt and reset)
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map(0x0000, 0x1fff).view(m_low_memory_view);
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// Microsoft Basic ROM
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map(0xc000, 0xdfff).rom();
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map(0xf000, 0xf7ff).rom();
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map(0xf800, 0xf8ff).ram();
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// Monitor ROM in the 8355 chip
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map(0xf000, 0xf7ff).rom().region(m_rom, 0);
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// 256 bytes of RAM of level A in the 8155 chip.
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map(0xf800, 0xf8ff).rw(m_i8155, FUNC(i8155_device::memory_r), FUNC(i8155_device::memory_w));
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// monitor ROM mirror
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m_low_memory_view[LOW_MEMORY_ROM_MIRROR_ENTRY](0x0000, 0x07ff).rom().region(m_rom, 0);
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// extended RAM
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m_low_memory_view[LOW_MEMORY_RAM_ENTRY](0x0000, 0x1fff).ram();
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}
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void exp85_state::exp85_io(address_map &map)
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{
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map.unmap_value_high();
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map.global_mask(0xff);
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map(0xf0, 0xf3).rw(I8355_TAG, FUNC(i8355_device::io_r), FUNC(i8355_device::io_w));
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map(0xf8, 0xfd).rw(I8155_TAG, FUNC(i8155_device::io_r), FUNC(i8155_device::io_w));
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// map(0xfe, 0xff).rw(I8279_TAG, FUNC(i8279_device::read), FUNC(i8279_device::write));
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map(0xf0, 0xf3).rw(m_i8355, FUNC(i8355_device::io_r), FUNC(i8355_device::io_w));
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map(0xf8, 0xfd).rw(m_i8155, FUNC(i8155_device::io_r), FUNC(i8155_device::io_w));
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}
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/* Input Ports */
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@ -111,6 +149,7 @@ void exp85_state::exp85_io(address_map &map)
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INPUT_CHANGED_MEMBER( exp85_state::trigger_reset )
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{
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m_maincpu->set_input_line(INPUT_LINE_RESET, newval ? CLEAR_LINE : ASSERT_LINE);
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m_low_memory_view.select(LOW_MEMORY_ROM_MIRROR_ENTRY);
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}
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INPUT_CHANGED_MEMBER( exp85_state::trigger_rst75 )
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@ -119,7 +158,6 @@ INPUT_CHANGED_MEMBER( exp85_state::trigger_rst75 )
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}
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static INPUT_PORTS_START( exp85 )
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PORT_START("SPECIAL")
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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)
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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)
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@ -201,6 +239,41 @@ void exp85_state::sod_w(int state)
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}
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}
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/* Memory mapping mgmt during reset and interrupt */
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void exp85_state::status_out(u8 status)
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{
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// In the real hardware this is monitored via the IO/M, S0, S1
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// and ALE output pins of the 8085.
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// Since these pins are not emulated, then we must explicitly get the internal
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// interrupt acknowledge state (0x23 or 0x26) and behave as the monitor expects.
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auto current_pc = m_maincpu->pc();
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if (status == 0x23 || status == 0x26)
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{
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// When an interrupt is triggered the low memory shall be set to the ROM mirror
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m_is_preparing_interrupt_call = true;
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m_low_memory_view.select(LOW_MEMORY_ROM_MIRROR_ENTRY);
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}
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else if (m_is_preparing_interrupt_call && (current_pc & 0xff00) == 0x0000)
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{
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// Avoids setting the lower memory back to RAM until
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// it branches to the interrupt handler.
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m_is_preparing_interrupt_call = false;
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}
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else if (!m_is_preparing_interrupt_call && (current_pc & 0xf000) == 0xf000)
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{
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// When the interrupt handler is executing and the address is >= 0xf000
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// the low memory is mapped to RAM
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m_low_memory_view.select(LOW_MEMORY_RAM_ENTRY);
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}
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}
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//**************************************************************************
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// INPUT PORTS
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//**************************************************************************
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/* Terminal Interface */
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static DEVICE_INPUT_DEFAULTS_START( terminal )
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@ -215,16 +288,47 @@ DEVICE_INPUT_DEFAULTS_END
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void exp85_state::machine_start()
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{
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/* setup memory banking */
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membank("bank1")->configure_entry(0, m_rom->base() + 0xf000);
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membank("bank1")->configure_entry(1, m_rom->base());
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membank("bank1")->set_entry(0);
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/* clear the trap line that is asserted on start */
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m_maincpu->set_input_line(I8085_TRAP_LINE, CLEAR_LINE);
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/* setup memory mirror switch */
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m_low_memory_view.select(LOW_MEMORY_ROM_MIRROR_ENTRY);
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save_item(NAME(m_tape_control));
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m_timer = timer_alloc(FUNC(exp85_state::trap_delay), this);
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}
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void exp85_state::to_change(int to)
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{
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// In the 8155 implementation the TIMER-OUT line (to) is
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// asserted by default on initialization; this generates a spurious exception
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// avoided here via an ignore flag.
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if (m_ignore_timer_out)
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{
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m_ignore_timer_out = false;
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return;
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}
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// The 8155 has a max TIMER-IN to TIMER-OUT delay of 400ns (datasheet page 3-256). In a real system
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// this delay was measured in ~70ns. This is enough for the next instruction cycle to start
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// and for the interrupt to be acknowledged one instruction later. This effect is fundamental
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// for the ROM monitor stepping functionality, since it depends heavily on interrupting when the
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// next instruction of the user program is being executed.
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// MAME allows to set a timer of 70ns but that is not enough to get the CPU scheduled for at least 1 cycle
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// before the interrupt is serviced, so we program a timer to expire beyond a full clock cycle.
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m_timer->adjust(m_i8155->clocks_to_attotime(2), to);
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}
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TIMER_CALLBACK_MEMBER(exp85_state::trap_delay)
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{
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// The 8155 TIMER-OUT line is connected to the TRAP input line of the 8085;
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// that line is set from the start high, and since there is no change in that line, the
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// interrup is never requested (datasheet, page 6-13).
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m_maincpu->set_input_line(I8085_TRAP_LINE, param == 1 ? ASSERT_LINE : CLEAR_LINE);
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}
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/* Machine Driver */
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void exp85_state::exp85(machine_config &config)
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{
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/* basic machine hardware */
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@ -233,17 +337,25 @@ void exp85_state::exp85(machine_config &config)
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m_maincpu->set_addrmap(AS_IO, &exp85_state::exp85_io);
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m_maincpu->in_sid_func().set(FUNC(exp85_state::sid_r));
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m_maincpu->out_sod_func().set(FUNC(exp85_state::sod_w));
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m_maincpu->out_status_func().set(FUNC(exp85_state::status_out));
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/* sound hardware */
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SPEAKER(config, "mono").front_center();
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SPEAKER_SOUND(config, m_speaker).add_route(ALL_OUTPUTS, "mono", 0.25);
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/* devices */
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I8155(config, I8155_TAG, 6.144_MHz_XTAL/2);
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i8355_device &i8355(I8355(config, I8355_TAG, 6.144_MHz_XTAL/2));
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i8355.in_pa().set(FUNC(exp85_state::i8355_a_r));
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i8355.out_pa().set(FUNC(exp85_state::i8355_a_w));
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// The Explorer-85 uses a 6.144MHz clock, but the Intel 8085 divides by 2 this
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// input frequency to give the processor internal operating frequency.
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// The bus is connected to the CLK (out) of the 8085, running also
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// at 6.144MHz divided by 2.
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I8155(config, m_i8155, 6.144_MHz_XTAL/2);
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m_i8155->out_to_callback().set(FUNC(exp85_state::to_change));
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I8355(config, m_i8355, 6.144_MHz_XTAL/2);
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m_i8355->in_pa().set(FUNC(exp85_state::i8355_a_r));
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m_i8355->out_pa().set(FUNC(exp85_state::i8355_a_w));
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CASSETTE(config, m_cassette);
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m_cassette->set_default_state(CASSETTE_STOPPED | CASSETTE_MOTOR_ENABLED | CASSETTE_SPEAKER_ENABLED);
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@ -251,31 +363,23 @@ void exp85_state::exp85(machine_config &config)
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RS232_PORT(config, "rs232", default_rs232_devices, "terminal").set_option_device_input_defaults("terminal", DEVICE_INPUT_DEFAULTS_NAME(terminal));
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/* internal ram */
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RAM(config, RAM_TAG).set_default_size("256").set_extra_options("4K");
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}
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/* ROMs */
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ROM_START( exp85 )
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ROM_REGION( 0x10000, I8085A_TAG, 0 )
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ROM_REGION( 0x10000, "u100", 0 ) // Microsoft Basic
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ROM_DEFAULT_BIOS("eia")
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ROM_LOAD( "c000.bin", 0xc000, 0x0800, CRC(73ce4aad) SHA1(2c69cd0b6c4bdc92f4640bce18467e4e99255bab) )
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ROM_LOAD( "c800.bin", 0xc800, 0x0800, CRC(eb3fdedc) SHA1(af92d07f7cb7533841b16e1176401363176857e1) )
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ROM_LOAD( "d000.bin", 0xd000, 0x0800, CRC(c10c4a22) SHA1(30588ba0b27a775d85f8c581ad54400c8521225d) )
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ROM_LOAD( "d800.bin", 0xd800, 0x0800, CRC(dfa43ef4) SHA1(56a7e7a64928bdd1d5f0519023d1594cacef49b3) )
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ROM_SYSTEM_BIOS( 0, "eia", "EIA Terminal" )
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ROMX_LOAD( "ex 85.u105", 0xf000, 0x0800, CRC(1a99d0d9) SHA1(57b6d48e71257bc4ef2d3dddc9b30edf6c1db766), ROM_BIOS(0) )
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ROM_SYSTEM_BIOS( 1, "hex", "Hex Keyboard" )
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ROMX_LOAD( "1kbd.u105", 0xf000, 0x0800, NO_DUMP, ROM_BIOS(1) )
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ROM_REGION( 0x800, I8355_TAG, ROMREGION_ERASE00 )
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/* ROM_DEFAULT_BIOS("terminal")
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ROM_SYSTEM_BIOS( 0, "terminal", "Terminal" )
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ROMX_LOAD( "eia.u105", 0xf000, 0x0800, CRC(1a99d0d9) SHA1(57b6d48e71257bc4ef2d3dddc9b30edf6c1db766), ROM_BIOS(0) )
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ROM_SYSTEM_BIOS( 1, "hexkbd", "Hex Keyboard" )
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ROMX_LOAD( "hex.u105", 0xf000, 0x0800, NO_DUMP, ROM_BIOS(1) )*/
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ROM_REGION( 0x800, "u105", 0 ) // Explorer 85 Monitor
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ROM_SYSTEM_BIOS( 0, "eia", "EIA Terminal" ) // Serial terminal ROM
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ROMX_LOAD( "ex 85.u105", 0x0000, 0x0800, CRC(1a99d0d9) SHA1(57b6d48e71257bc4ef2d3dddc9b30edf6c1db766), ROM_BIOS(0) )
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ROM_SYSTEM_BIOS( 1, "hex", "Hex Keyboard" ) // Keypad ROM (not available)
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ROMX_LOAD( "1kbd.u105", 0x0000, 0x0800, NO_DUMP, ROM_BIOS(1) )
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ROM_END
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} // anonymous namespace
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