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author Aaron Giles <aaron@aarongiles.com>2021-03-02 01:32:54 -0800
committer Aaron Giles <aaron@aarongiles.com>2021-03-02 01:32:54 -0800
commitc89cbcd0e599d7baca6d294e451fcd4249b4a74e (patch)
treebc120ef39a1ea6c154eec670d5ef46bdc54eb48e /src/devices
parente35f24a48772987d5a3c9d28e44f7aa245d3e070 (diff)
Fix YM synchronization in Seibu sound device.
Diffstat (limited to 'src/devices')
-rw-r--r--src/devices/sound/ymfm.cpp11
-rw-r--r--src/devices/sound/ymfm.h1
2 files changed, 12 insertions, 0 deletions
diff --git a/src/devices/sound/ymfm.cpp b/src/devices/sound/ymfm.cpp
index 55282f3c18b..4c4cc14ac48 100644
--- a/src/devices/sound/ymfm.cpp
+++ b/src/devices/sound/ymfm.cpp
@@ -1261,6 +1261,7 @@ ymfm_engine_base<RegisterType>::ymfm_engine_base(device_t &device) :
m_irq_mask(STATUS_TIMERA | STATUS_TIMERB),
m_irq_state(0),
m_busy_end(attotime::zero),
+ m_last_irq_update(attotime::zero),
m_timer{ nullptr, nullptr },
m_irq_handler(device),
m_regdata(RegisterType::REGISTERS),
@@ -1632,7 +1633,17 @@ void ymfm_engine_base<RegisterType>::check_interrupts()
// if changed, signal the new state
if (old_state != m_irq_state && !m_irq_handler.isnull())
+ {
+ // if writes to registers aren't synchronized, it is possible to induce
+ // scheduling errors handling IRQs; ensure that all IRQ handler updates
+ // are monotonically increasing in time
+ attotime curtime = m_device.machine().time();
+ if (m_last_irq_update > curtime)
+ fatalerror("IRQ signalling time went backwards; writes need to be synchronized");
+ m_last_irq_update = curtime;
+
m_irq_handler(m_irq_state ? ASSERT_LINE : CLEAR_LINE);
+ }
}
diff --git a/src/devices/sound/ymfm.h b/src/devices/sound/ymfm.h
index be9959a2ef5..18c0afa3d35 100644
--- a/src/devices/sound/ymfm.h
+++ b/src/devices/sound/ymfm.h
@@ -799,6 +799,7 @@ private:
u8 m_irq_mask; // mask of which bits signal IRQs
u8 m_irq_state; // current IRQ state
attotime m_busy_end; // end of the busy time
+ attotime m_last_irq_update; // time of last IRQ update
emu_timer *m_timer[2]; // our two timers
devcb_write_line m_irq_handler; // IRQ callback
std::unique_ptr<ymfm_channel<RegisterType>> m_channel[RegisterType::CHANNELS]; // channel pointers