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mac: Correctly sync the main cpu to the via. Fixes the floppy writes, probably need to be propagated to other handlers

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This commit is contained in:
Olivier Galibert 2021-02-22 18:34:17 +01:00
parent c0e8eb5928
commit d8c697eb85
2 changed files with 34 additions and 5 deletions
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1
src/mame/includes/mac.h
View File

@ -307,6 +307,7 @@ private:
void rbv_recalc_irqs();
void update_volume();
void mac_via_sync();
uint16_t mac_via_r(offs_t offset);
void mac_via_w(offs_t offset, uint16_t data, uint16_t mem_mask = ~0);
uint16_t mac_via2_r(offs_t offset);

38
src/mame/machine/mac.cpp
View File

@ -624,6 +624,9 @@ WRITE_LINE_MEMBER(mac_state::mac_scsi_irq)
* *************************************************************************/
uint16_t mac_state::mac_scc_r(offs_t offset)
{
if (!machine().side_effects_disabled())
mac_via_sync();
uint16_t result;
result = m_scc->reg_r(offset);
@ -632,11 +635,13 @@ uint16_t mac_state::mac_scc_r(offs_t offset)
void mac_state::mac_scc_w(offs_t offset, uint16_t data)
{
mac_via_sync();
m_scc->reg_w(offset, data);
}
void mac_state::mac_scc_2_w(offs_t offset, uint16_t data)
{
mac_via_sync();
m_scc->reg_w(offset, data >> 8);
}
@ -925,8 +930,34 @@ WRITE_LINE_MEMBER(mac_state::mac_via_irq)
set_via_interrupt(state);
}
void mac_state::mac_via_sync()
{
// The via runs at 783.36KHz while the main cpu runs at 15MHz or
// more, so we need to sync the access with the via clock. Plus
// the whole access takes half a (via) cycle and ends when synced
// with the main cpu again.
// Get the main cpu time
u64 cycle = m_maincpu->total_cycles();
// Get the number of the cycle the via is in at that time
u64 via_cycle = cycle * m_via1->clock() / m_maincpu->clock();
// The access is going to start at via_cycle+1 and end at
// via_cycle+1.5, compute what that means in maincpu cycles (the
// +1 rounds up, since the clocks are too different to ever be
// synced).
u64 main_cycle = (via_cycle*2+3) * m_maincpu->clock() / (2*m_via1->clock()) + 1;
// Finally adjust the main cpu icount as needed.
m_maincpu->adjust_icount(-int(main_cycle - cycle));
}
uint16_t mac_state::mac_via_r(offs_t offset)
{
if (!machine().side_effects_disabled())
mac_via_sync();
uint16_t data;
offset >>= 8;
@ -936,14 +967,13 @@ uint16_t mac_state::mac_via_r(offs_t offset)
logerror("mac_via_r: offset=0x%02x\n", offset);
data = m_via1->read(offset);
if (!machine().side_effects_disabled())
m_maincpu->adjust_icount(m_via_cycles);
return (data & 0xff) | (data << 8);
}
void mac_state::mac_via_w(offs_t offset, uint16_t data, uint16_t mem_mask)
{
mac_via_sync();
offset >>= 8;
offset &= 0x0f;
@ -954,8 +984,6 @@ void mac_state::mac_via_w(offs_t offset, uint16_t data, uint16_t mem_mask)
m_via1->write(offset, data & 0xff);
if (ACCESSING_BITS_8_15)
m_via1->write(offset, (data >> 8) & 0xff);
m_maincpu->adjust_icount(m_via_cycles);
}
/* *************************************************************************