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implementing a simple adder and subtractor

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Thiago Auler 2017-11-14 15:54:56 -02:00 committed by GitHub
parent 1a7acdaf95
commit 57159c7484
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1 changed files with 29 additions and 0 deletions
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29
src/opcodes.c
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@ -67,6 +67,35 @@ void fetch_operand()
}
}
void adjustNZ(db a)
{
if (a == 0) { Z_SET; } else { Z_UNSET;}
a = a >> 7;
if (a == 0) { N_SET; } else { N_UNSET; }
}
db adder(db a, db b)
{
db r = a + b;
// todo: adjust carry flag
// todo: adjust overflow flag
adjustNZ(r);
return r;
}
db subtractor(db a, db b)
{
db r = a - b;
// todo: adjust carry flag
// todo: adjust overflow flag
adjustNZ(r);
return r;
}
void adc()
{
// add memory to accumalator with carry