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WOZ: Fix for reading write-protect from data register (#1078)

This commit is contained in:
tomcw 2022-04-18 21:13:41 +01:00
parent 03aec01086
commit cb37dd300b
1 changed files with 6 additions and 3 deletions
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9
source/Disk.cpp
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@ -1595,13 +1595,14 @@ void __stdcall Disk2InterfaceCard::LoadWriteProtect(WORD, WORD, BYTE write, BYTE
// . write mode doesn't prevent reading write protect (GH#537):
// "If for some reason the above write protect check were entered with the READ/WRITE switch in WRITE,
// the write protect switch would still be read correctly" (UTAIIe page 9-21)
// . Sequencer "SR" (Shift Right) command only loads QA (bit7) of data register (UTAIIe page 9-21)
// . Sequencer "SR" (Shift Right) command shifts the data register right and loads QA (bit7) with write protect (UTAIIe page 9-21)
// . A read or write will shift 'write protect' in QA.
// . The LSS saturates the data register before the CPU can read an intermediate value: so set to 0xFF or 0x00 (GH#1078)
FloppyDisk& floppy = m_floppyDrive[m_currDrive].m_disk;
if (floppy.m_bWriteProtected)
m_floppyLatch |= 0x80;
m_floppyLatch = 0xFF;
else
m_floppyLatch &= 0x7F;
m_floppyLatch = 0x00;
if (m_writeStarted) // Prevent ResetLogicStateSequencer() from resetting m_writeStarted
return;
@ -1618,6 +1619,8 @@ void __stdcall Disk2InterfaceCard::LoadWriteProtect(WORD, WORD, BYTE write, BYTE
// UpdateBitStreamPosition() must be done before ResetLSS, as the former clears m_resetSequencer (and the latter sets it).
// . Commando.woz is sensitive to this. EG. It can crash after pressing 'J' (1 failure in 20 reboot repeats)
ResetLogicStateSequencer(); // reset sequencer (UTAIIe page 9-21)
m_shiftReg = m_floppyLatch;
}
}