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Fixed: attempting to read the screen start address no longer alters it.

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This commit is contained in:
Thomas Harte 2016-03-13 18:50:23 -04:00
parent 1c4acfb599
commit bc554dedf7
1 changed files with 10 additions and 6 deletions
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16
Machines/Electron/Electron.cpp
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@ -124,14 +124,18 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
case 0x1: case 0x1:
break; break;
case 0x2: case 0x2:
printf("%02x to [2] mutates %04x ", *value, _startScreenAddress); if(!isReadOperation(operation))
_startScreenAddress = (_startScreenAddress & 0xfe00) | (uint16_t)(((*value) & 0xe0) << 1); {
printf("into %04x\n", _startScreenAddress); _startScreenAddress = (_startScreenAddress & 0xfe00) | (uint16_t)(((*value) & 0xe0) << 1);
if(!_startScreenAddress) _startScreenAddress |= 0x8000;
}
break; break;
case 0x3: case 0x3:
printf("%02x to [3] mutates %04x ", *value, _startScreenAddress); if(!isReadOperation(operation))
_startScreenAddress = (_startScreenAddress & 0x01ff) | (uint16_t)(((*value) & 0x3f) << 9); {
printf("into %04x\n", _startScreenAddress); _startScreenAddress = (_startScreenAddress & 0x01ff) | (uint16_t)(((*value) & 0x3f) << 9);
if(!_startScreenAddress) _startScreenAddress |= 0x8000;
}
break; break;
case 0x4: case 0x4:
if(isReadOperation(operation)) if(isReadOperation(operation))