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ymfm: Correct for free-running timer B multipler (#8988)

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Aaron Giles 2021-12-16 05:16:48 -08:00 committed by GitHub
parent 27c64d0512
commit d187a28fad
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2 changed files with 16 additions and 6 deletions
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3
3rdparty/ymfm/src/ymfm_fm.h vendored
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@ -426,7 +426,7 @@ protected:
void assign_operators();
// update the state of the given timer
void update_timer(uint32_t which, uint32_t enable);
void update_timer(uint32_t which, uint32_t enable, int32_t delta_clocks);
// internal state
ymfm_interface &m_intf; // reference to the system interface
@ -436,6 +436,7 @@ protected:
uint8_t m_irq_mask; // mask of which bits signal IRQs
uint8_t m_irq_state; // current IRQ state
uint8_t m_timer_running[2]; // current timer running state
uint8_t m_total_clocks; // low 8 bits of the total number of clocks processed
uint32_t m_active_channels; // mask of active channels (computed by prepare)
uint32_t m_modified_channels; // mask of channels that have been modified
uint32_t m_prepare_count; // counter to do periodic prepare sweeps

19
3rdparty/ymfm/src/ymfm_fm.ipp vendored
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@ -1227,6 +1227,7 @@ void fm_engine_base<RegisterType>::save_restore(ymfm_saved_state &state)
state.save_restore(m_irq_state);
state.save_restore(m_timer_running[0]);
state.save_restore(m_timer_running[1]);
state.save_restore(m_total_clocks);
// save the register/family data
m_regs.save_restore(state);
@ -1252,6 +1253,9 @@ void fm_engine_base<RegisterType>::save_restore(ymfm_saved_state &state)
template<class RegisterType>
uint32_t fm_engine_base<RegisterType>::clock(uint32_t chanmask)
{
// update the clock counter
m_total_clocks++;
// if something was modified, prepare
// also prepare every 4k samples to catch ending notes
if (m_modified_channels != 0 || m_prepare_count++ >= 4096)
@ -1428,7 +1432,7 @@ void fm_engine_base<RegisterType>::assign_operators()
//-------------------------------------------------
template<class RegisterType>
void fm_engine_base<RegisterType>::update_timer(uint32_t tnum, uint32_t enable)
void fm_engine_base<RegisterType>::update_timer(uint32_t tnum, uint32_t enable, int32_t delta_clocks)
{
// if the timer is live, but not currently enabled, set the timer
if (enable && !m_timer_running[tnum])
@ -1436,6 +1440,9 @@ void fm_engine_base<RegisterType>::update_timer(uint32_t tnum, uint32_t enable)
// period comes from the registers, and is different for each
uint32_t period = (tnum == 0) ? (1024 - m_regs.timer_a_value()) : 16 * (256 - m_regs.timer_b_value());
// caller can also specify a delta to account for other effects
period += delta_clocks;
// reset it
m_intf.ymfm_set_timer(tnum, period * OPERATORS * m_clock_prescale);
m_timer_running[tnum] = 1;
@ -1472,7 +1479,7 @@ void fm_engine_base<RegisterType>::engine_timer_expired(uint32_t tnum)
// reset
m_timer_running[tnum] = false;
update_timer(tnum, 1);
update_timer(tnum, 1, 0);
}
@ -1530,9 +1537,11 @@ void fm_engine_base<RegisterType>::engine_mode_write(uint8_t data)
reset_mask |= RegisterType::STATUS_TIMERA;
set_reset_status(0, reset_mask);
// load timers
update_timer(1, m_regs.load_timer_b());
update_timer(0, m_regs.load_timer_a());
// load timers; note that timer B gets a small negative adjustment because
// the *16 multiplier is free-running, so the first tick of the clock
// is a bit shorter
update_timer(1, m_regs.load_timer_b(), -(m_total_clocks & 15));
update_timer(0, m_regs.load_timer_a(), 0);
}
}