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Merge pull request #813 from Atari2/fix-sa1-division 

Fix dvision routine on SA-1 returns the wrong reminder (and quotient) on negative dividends
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bearoso 2023-02-04 11:47:56 -06:00 committed by GitHub
parent f6197644e8 11e1435689
commit a2e0580992
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1 changed files with 3 additions and 2 deletions
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sa1.cpp
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@ -563,8 +563,9 @@ void S9xSetSA1 (uint8 byte, uint32 address)
{ {
int16 dividend = (int16) SA1.op1; int16 dividend = (int16) SA1.op1;
uint16 divisor = (uint16) SA1.op2; uint16 divisor = (uint16) SA1.op2;
uint16 remainder = (dividend >= 0) ? dividend % divisor : (dividend % divisor) + divisor; uint32 dividend_ext = dividend + (uint32)divisor * 65536;
uint16 quotient = (dividend - remainder) / divisor; uint16 remainder = dividend_ext % divisor;
uint16 quotient = dividend_ext / divisor;
SA1.sum = (remainder << 16) | quotient; SA1.sum = (remainder << 16) | quotient;
} }