Apple-2-Tools/AppleWin
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Only T1 (and not T2) interprets a latch of 0x0000 as 0x10000.

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There is partial T2 support: IFR.T2 gets set on underflow.
But T2 reads as 0x00FF.
This commit is contained in:
tomcw 2023-04-10 09:43:22 +01:00
parent 3a7ff2063b
commit e5957beb37
2 changed files with 4 additions and 6 deletions
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8
source/6522.cpp
View File

@ -110,7 +110,7 @@ USHORT SY6522::SetTimerSyncEvent(BYTE reg, USHORT timerLatch)
if (syncEvent->m_active)
g_SynchronousEventMgr.Remove(syncEvent->m_id);
if (m_isMegaAudio && timerLatch == 0x0000) timerLatch = 0xFFFF; // Probably should be 0x10000, but 0xFFFF is good enough
if (m_isMegaAudio && reg == rT1CH && timerLatch == 0x0000) timerLatch = 0xFFFF; // Probably should be 0x10000, but 0xFFFF is good enough
const UINT kMegaAudioAdjust = m_isMegaAudio ? 1 : 0; // MegaAudio asserts IRQ 1 cycle late!
syncEvent->SetCycles(timerLatch + kExtraTimerCycles + opcodeCycleAdjust + kMegaAudioAdjust);
g_SynchronousEventMgr.Insert(syncEvent);
@ -177,12 +177,10 @@ void SY6522::Write(BYTE nReg, BYTE nValue)
m_regs.TIMER1_LATCH.h = nValue;
break;
case 0x08: // TIMER2L
if (m_isMegaAudio) break; // MegaAudio: Assume no Timer2
m_regs.TIMER2_LATCH.l = nValue;
break;
case 0x09: // TIMER2H
{
if (m_isMegaAudio) break; // MegaAudio: Assume no Timer2
UpdateIFR(IxR_TIMER2); // Clear Timer2 Interrupt Flag
m_regs.TIMER2_LATCH.h = nValue; // NB. Real 6522 doesn't have TIMER2_LATCH.h
m_regs.TIMER2_COUNTER.w = SetTimerSyncEvent(nReg, m_regs.TIMER2_LATCH.w);
@ -372,13 +370,13 @@ BYTE SY6522::Read(BYTE nReg)
nValue = m_regs.TIMER1_LATCH.h;
break;
case 0x08: // TIMER2L
if (m_isMegaAudio) break; // MegaAudio: Assume no Timer2
nValue = GetTimer2Counter(nReg) & 0xff;
UpdateIFR(IxR_TIMER2);
if (m_isMegaAudio) nValue = 0xFF; // MegaAudio: Timer2 just reads as $00FF
break;
case 0x09: // TIMER2H
if (m_isMegaAudio) break; // MegaAudio: Assume no Timer2
nValue = GetTimer2Counter(nReg) >> 8;
if (m_isMegaAudio) nValue = 0x00; // MegaAudio: Timer2 just reads as $00FF
break;
case 0x0a: // SERIAL_SHIFT
break;

2
source/Mockingboard.cpp
View File

@ -299,7 +299,7 @@ void MockingboardCard::AY8910_Write(BYTE subunit, BYTE ay, BYTE value)
}
else
{
r6522.SetRegORA(0x00); // Reads not supported. TODO: find out what value is actually read.
r6522.SetRegORA(0x00); // Reads not supported.
}
if (m_phasorEnable && m_phasorMode == PH_Phasor) // GH#1192