sinclair/sprinter.cpp: update #12269
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holub
commented
Apr 17, 2024
holub
commented
- accelerator writes through page fd only in COPY mode
- io access 1f (z84 int) available through replacing to 0f
- hold IRQ for 32 clocks (unscaled)
- accelerator writes through page fd only in COPY mode - io access 1f (z84) available through replacing to 0f - hold IRQ for 32 clocks (unscaled)
| TIMER_CALLBACK_MEMBER(sprinter_state::irq_on) | ||
| { | ||
| m_maincpu->pulse_input_line(INPUT_LINE_IRQ0, attotime::from_ticks(26, m_maincpu->clock())); | ||
| if (!m_hold_irq) | ||
| { | ||
| m_maincpu->set_input_line(INPUT_LINE_IRQ0, ASSERT_LINE); | ||
| m_irq_off_timer->adjust(attotime::from_ticks(32, m_maincpu->unscaled_clock())); | ||
| } | ||
| update_int(false); | ||
| } |
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Should this interrupt continue to be held for the full 32 cycles even if there’s an interrupt acknowledge cycle, or should an interrupt acknowledge cycle clear this interrupt as well as the other one? (The implementation currently does the latter – clears both kinds of interrupt on an interrupt acknowledge cycle.)
src/mame/sinclair/sprinter.cpp
Outdated
| TIMER_CALLBACK_MEMBER(sprinter_state::irq_off) | ||
| { | ||
| m_hold_irq = 0; | ||
| m_maincpu->set_input_line(INPUT_LINE_IRQ0, CLEAR_LINE); | ||
| } |
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This can be called two ways now – from m_irq_off_timer expiring, and from an interrupt acknowledge cycle on the main CPU. If it’s called from an interrupt acknowledge cycle, should it cancel the timer? If it doesn’t, this sequence of events can happen:
irq_onasserts interrupt and startsm_irq_off_timer- Interrupt acknowledge cycle causes
irq_offto be called, clearing interrupt m_irq_off_timerfires, causingirq_offto be called again
It’s probably harmless given what it’s doing, but it will go through another timer update and then go through the scheduler again to clear the IRQ line.
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Please hold on merging this. I need to double check this IRQ behaviour |
|
False alarm. It's good to go. |
