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6522 timer IRQs were triggering one cycle too late.

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This commit is contained in:
Stephen White 2019-04-28 15:50:57 +10:00
parent 47355edeff
commit 520d6e6540
2 changed files with 23 additions and 27 deletions
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48
src/m6522.cpp
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@ -147,22 +147,6 @@ void m6522::Execute()
{
t1c.value = t1l.value;
t1TimedOut = false;
if (t1FreeRun)
{
if (t1FreeRunIRQsOn)
SetInterrupt(IR_T1);
}
else
{
if (!t1OneShotTriggeredIRQ)
{
t1OneShotTriggeredIRQ = true;
SetInterrupt(IR_T1);
}
// At this time the counter will continue to decrement at system clock rate.
// This allows the system processor to read the contents of the counter to determine the time since interrupt.
}
}
else if (t1Ticking && !t1Reload && !t1c.value--)
{
@ -170,6 +154,9 @@ void m6522::Execute()
if (t1FreeRun)
{
if (t1FreeRunIRQsOn)
SetInterrupt(IR_T1);
if (t1l.value > 1) // A real VIA will not flip PB7 if the frequency is above a certain (ie 1 cycle) threshold
{
t1_pb7 = !t1_pb7;
@ -189,6 +176,9 @@ void m6522::Execute()
{
if (!t1OneShotTriggeredIRQ)
{
t1OneShotTriggeredIRQ = true;
SetInterrupt(IR_T1);
if (t1OutPB7)
{
// PB7 was set low on the write to T1CH now the signal on PB7 will go high
@ -216,16 +206,7 @@ void m6522::Execute()
t2TimedOut = false;
// In both modes the interrupt is only set once
if (!t2OneShotTriggeredIRQ)
{
t2OneShotTriggeredIRQ = true;
SetInterrupt(IR_T2);
}
else
{
// At this time the counter will continue to decrement at system clock rate or PB6 negative edge counts (depending upon mode)
// This allows the system processor to read the contents of the counter to determine the time since interrupt.
}
if ((auxiliaryControlRegister & 0xc) == 4) // shift by timer 2?
{
@ -302,6 +283,21 @@ void m6522::Execute()
{
t2Reload = false;
}
if (t2TimedOut)
{
// In both modes the interrupt is only set once
if (!t2OneShotTriggeredIRQ)
{
t2OneShotTriggeredIRQ = true;
SetInterrupt(IR_T2);
}
else
{
// At this time the counter will continue to decrement at system clock rate or PB6 negative edge counts (depending upon mode)
// This allows the system processor to read the contents of the counter to determine the time since interrupt.
}
}
}
pb6Old = pb6;
t2CountingPB6ModeOld = t2CountingPB6Mode;

2
src/m6522.h
View file

@ -29,7 +29,7 @@ class m6522
// PB 1 data out
// PB 2 clock in
// PB 3 clock out
// PB 4 ATNA
// PB 4 ATNA out
// PB 5,6 device address
// PB 7,CA1 ATN IN