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m20: Eliminate HOLD_LINE (nw)

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This commit is contained in:
AJR 2020-04-19 17:51:43 -04:00
parent 928b8f61d2
commit db698f6c0a
1 changed files with 13 additions and 7 deletions
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20
src/mame/drivers/m20.cpp
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@ -120,6 +120,7 @@ private:
DECLARE_FLOPPY_FORMATS( floppy_formats ); DECLARE_FLOPPY_FORMATS( floppy_formats );
uint16_t viack_r(); uint16_t viack_r();
uint16_t nviack_r();
}; };
@ -226,8 +227,7 @@ WRITE_LINE_MEMBER( m20_state::kbd_clock_tick_w )
WRITE_LINE_MEMBER( m20_state::timer_tick_w ) WRITE_LINE_MEMBER( m20_state::timer_tick_w )
{ {
/* Using HOLD_LINE is not completely correct: /* The output of the 8253 is connected to a 74LS74 flop chip.
* The output of the 8253 is connected to a 74LS74 flop chip.
* The output of the flop chip is connected to NVI CPU input. * The output of the flop chip is connected to NVI CPU input.
* The flop is reset by a 1:8 decoder which compares CPU ST0-ST3 * The flop is reset by a 1:8 decoder which compares CPU ST0-ST3
* outputs to detect an interrupt acknowledge transaction. * outputs to detect an interrupt acknowledge transaction.
@ -236,7 +236,8 @@ WRITE_LINE_MEMBER( m20_state::timer_tick_w )
*/ */
if(m_apb) if(m_apb)
m_apb->nvi_w(state); m_apb->nvi_w(state);
m_maincpu->set_input_line(z8001_device::NVI_LINE, state ? HOLD_LINE /*ASSERT_LINE*/ : CLEAR_LINE); if(state)
m_maincpu->set_input_line(z8001_device::NVI_LINE, ASSERT_LINE);
} }
@ -719,11 +720,9 @@ void m20_state::m20_io(address_map &map)
map(0x80, 0x87).rw(m_i8255, FUNC(i8255_device::read), FUNC(i8255_device::write)).umask16(0x00ff); map(0x80, 0x87).rw(m_i8255, FUNC(i8255_device::read), FUNC(i8255_device::write)).umask16(0x00ff);
map(0xa1, 0xa1).rw(m_kbdi8251, FUNC(i8251_device::data_r), FUNC(i8251_device::data_w)); map(0xa0, 0xa3).rw(m_kbdi8251, FUNC(i8251_device::read), FUNC(i8251_device::write)).umask16(0x00ff);
map(0xa3, 0xa3).rw(m_kbdi8251, FUNC(i8251_device::status_r), FUNC(i8251_device::control_w));
map(0xc1, 0xc1).rw(m_ttyi8251, FUNC(i8251_device::data_r), FUNC(i8251_device::data_w)); map(0xc0, 0xc3).rw(m_ttyi8251, FUNC(i8251_device::read), FUNC(i8251_device::write)).umask16(0x00ff);
map(0xc3, 0xc3).rw(m_ttyi8251, FUNC(i8251_device::status_r), FUNC(i8251_device::control_w));
map(0x120, 0x127).rw("pit8253", FUNC(pit8253_device::read), FUNC(pit8253_device::write)).umask16(0x00ff); map(0x120, 0x127).rw("pit8253", FUNC(pit8253_device::read), FUNC(pit8253_device::write)).umask16(0x00ff);
@ -737,6 +736,12 @@ uint16_t m20_state::viack_r()
return m_i8259->acknowledge()<<1; return m_i8259->acknowledge()<<1;
} }
uint16_t m20_state::nviack_r()
{
m_maincpu->set_input_line(z8001_device::NVI_LINE, CLEAR_LINE);
return 0xffff;
}
WRITE_LINE_MEMBER(m20_state::int_w) WRITE_LINE_MEMBER(m20_state::int_w)
{ {
if(m_apb && !m_apb->halted()) if(m_apb && !m_apb->halted())
@ -794,6 +799,7 @@ void m20_state::m20(machine_config &config)
m_maincpu->set_addrmap(AS_DATA, &m20_state::m20_data_mem); m_maincpu->set_addrmap(AS_DATA, &m20_state::m20_data_mem);
m_maincpu->set_addrmap(AS_IO, &m20_state::m20_io); m_maincpu->set_addrmap(AS_IO, &m20_state::m20_io);
m_maincpu->viack().set(FUNC(m20_state::viack_r)); m_maincpu->viack().set(FUNC(m20_state::viack_r));
m_maincpu->nviack().set(FUNC(m20_state::nviack_r));
RAM(config, RAM_TAG).set_default_size("160K").set_default_value(0).set_extra_options("128K,192K,224K,256K,384K,512K"); RAM(config, RAM_TAG).set_default_size("160K").set_default_value(0).set_extra_options("128K,192K,224K,256K,384K,512K");