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system1: correct mcu t0 pin

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This commit is contained in:
hap 2024-11-12 16:30:34 +01:00
parent 28cb15d131
commit 671e52155e
2 changed files with 8 additions and 11 deletions
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17
src/mame/sega/system1.cpp
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@ -572,7 +572,7 @@ void system1_state::mcu_control_w(u8 data)
{
/*
Bit 7 -> connects to TD62003 pins 5 & 6 @ IC151
Bit 6 -> via PLS153, when high, asserts the BUSREQ signal, halting the Z80
Bit 6 -> via PLS153, when high, asserts the BUSRQ signal, halting the Z80
Bit 5 -> n/c
Bit 4 -> (with bit 3) Memory select: 0=Z80 program space, 1=banked ROM, 2=Z80 I/O space, 3=watchdog?
Bit 3 ->
@ -635,16 +635,12 @@ u8 system1_state::mcu_io_r(offs_t offset)
}
TIMER_DEVICE_CALLBACK_MEMBER(system1_state::mcu_t0_callback)
IRQ_CALLBACK_MEMBER(system1_state::mcu_t0_callback)
{
/* The T0 line is clocked by something; if it is not clocked fast
enough, the MCU will fail; on shtngmst this happens after 3
VBLANKs without a tick.
choplift is even more picky about it, affecting scroll speed
*/
m_mcu->set_input_line(MCS51_T0_LINE, ASSERT_LINE);
m_mcu->set_input_line(MCS51_T0_LINE, CLEAR_LINE);
return 0xff;
}
@ -2524,11 +2520,12 @@ void system1_state::mcu(machine_config &config)
config.set_maximum_quantum(attotime::from_hz(m_maincpu->clock() / 16));
TIMER(config, "mcu_t0", 0).configure_periodic(FUNC(system1_state::mcu_t0_callback), attotime::from_usec(2500));
// This interrupt is driven by pin 15 of a PAL16R4 (315-5138 on Choplifter), based on the vertical count.
// The actual duty cycle likely differs from VBLANK, which is another output from the same PAL.
m_screen->screen_vblank().set_inputline("mcu", MCS51_INT0_LINE);
// bus controller INTACK pin clocks MCU T0
m_maincpu->set_irq_acknowledge_callback(FUNC(system1_state::mcu_t0_callback));
}
// alternate program map with RAM/collision swapped

2
src/mame/sega/system1.h
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@ -187,7 +187,7 @@ protected:
// misc functions
TIMER_DEVICE_CALLBACK_MEMBER(soundirq_gen);
TIMER_DEVICE_CALLBACK_MEMBER(mcu_t0_callback);
IRQ_CALLBACK_MEMBER(mcu_t0_callback);
void bank44_custom_w(u8 data);
void bank0c_custom_w(u8 data);