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st2204: Improve timer synchronization (nw)

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This commit is contained in:
AJR 2019-11-07 18:23:39 -05:00
parent c0cc6cc7bd
commit 15d97d90f6
4 changed files with 24 additions and 13 deletions
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28
src/devices/cpu/m6502/st2204.cpp
View File

@ -264,6 +264,12 @@ TIMER_CALLBACK_MEMBER(st2204_device::t0_interrupt)
m_t0_timer->adjust(cycles_to_attotime((256 - m_tcntr[0]) * tclk_pres_div(m_tmode[0] & 0x07)));
}
void st2204_device::t0_start()
{
u32 div = tclk_pres_div(m_tmode[0] & 0x07);
m_t0_timer->adjust(cycles_to_attotime((255 - m_tcntr[0]) * div + div - (pres_count() & (div - 1))));
}
u8 st2204_device::t0m_r()
{
return m_tmode[0];
@ -271,20 +277,18 @@ u8 st2204_device::t0m_r()
void st2204_device::t0m_w(u8 data)
{
if ((data & 0x27) != (m_tmode[0] & 0x27) && (m_prs & 0x60) == 0x40)
u8 t0m_old = std::exchange(m_tmode[0], data & 0x37);
if ((data & 0x27) != (t0m_old & 0x27) && (m_prs & 0x60) == 0x40)
{
// forced update
m_tcntr[0] = t0c_r();
if (BIT(data, 5))
{
u32 div = tclk_pres_div(data & 0x07);
m_t0_timer->adjust(cycles_to_attotime((255 - m_tcntr[0]) * div) + cycles_to_attotime(div - (m_pres_base & (div - 1))));
}
else if (BIT(m_tmode[0], 5))
t0_start();
else if (BIT(t0m_old, 5))
m_t0_timer->adjust(attotime::never);
}
m_tmode[0] = data & 0x37;
}
u8 st2204_device::t0c_r()
@ -294,7 +298,7 @@ u8 st2204_device::t0c_r()
else
{
u32 div = tclk_pres_div(m_tmode[0] & 0x07);
return 256 - std::max((attotime_to_cycles(m_t0_timer->remaining()) + div - 1) / div, u64(1));
return 255 - u8(attotime_to_cycles(m_t0_timer->remaining()) / div);
}
}
@ -302,7 +306,7 @@ void st2204_device::t0c_w(u8 data)
{
m_tcntr[0] = m_tload[0] = data;
if ((m_prs & 0x60) == 0x40 && BIT(m_tmode[0], 5))
m_t0_timer->adjust(cycles_to_attotime((256 - data) * tclk_pres_div(m_tmode[0] & 0x07)));
t0_start();
}
u8 st2204_device::t1m_r()
@ -327,8 +331,8 @@ void st2204_device::t1c_w(u8 data)
void st2204_device::st2xxx_tclk_start()
{
u32 div = tclk_pres_div(m_tmode[0] & 0x07);
m_t0_timer->adjust(cycles_to_attotime((255 - m_tcntr[0]) * div) + cycles_to_attotime(div - (m_pres_base & (div - 1))));
if (BIT(m_tmode[0], 5))
t0_start();
}
void st2204_device::st2xxx_tclk_stop()

1
src/devices/cpu/m6502/st2204.h
View File

@ -73,6 +73,7 @@ private:
u8 pmcr_r();
void pmcr_w(u8 data);
TIMER_CALLBACK_MEMBER(t0_interrupt);
void t0_start();
u8 t0m_r();
void t0m_w(u8 data);
u8 t0c_r();

7
src/devices/cpu/m6502/st2xxx.cpp
View File

@ -396,9 +396,14 @@ u32 st2xxx_device::tclk_pres_div(u8 mode) const
return 0x8000 >> (mode * 2);
}
u16 st2xxx_device::pres_count() const
{
return (m_pres_base + ((m_prs & 0x60) == 0x40 ? attotime_to_cycles(machine().time() - m_pres_started) : 0));
}
u8 st2xxx_device::prs_r()
{
return (m_pres_base + ((m_prs & 0x60) == 0x40 ? attotime_to_cycles(machine().time() - m_pres_started) : 0)) & 0xff;
return pres_count() & 0xff;
}
void st2xxx_device::prs_w(u8 data)

1
src/devices/cpu/m6502/st2xxx.h
View File

@ -168,6 +168,7 @@ protected:
void btclr_all_w(u8 data);
u32 tclk_pres_div(u8 mode) const;
u16 pres_count() const;
u8 prs_r();
void prs_w(u8 data);