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SBC(B) flag fixes

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folkert van heusden 2022-04-01 22:10:16 +02:00
parent dd634fcde8
commit 63c4697dee
1 changed files with 16 additions and 17 deletions
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33
cpu.cpp
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@ -865,36 +865,35 @@ bool cpu::single_operand_instructions(const uint16_t instr)
case 0b000101110: { // SBC/SBCB
if (dst_mode == 0) {
uint16_t v = getRegister(dst_reg, false);
uint16_t add = word_mode ? v & 0xff00 : 0;
bool org_c = getPSW_c();
uint16_t v = getRegister(dst_reg, false);
const uint16_t vo = v;
uint16_t add = word_mode ? v & 0xff00 : 0;
bool org_c = getPSW_c();
v = (v - org_c) & (word_mode ? 0xff : 0xffff);
v |= add;
setPSW_n(SIGN(v, word_mode));
setPSW_z(IS_0(v, word_mode));
setPSW_v((word_mode ? (v & 0xff) == 0x7f : v == 0x7fff) && org_c);
setPSW_c((word_mode ? (v & 0xff) == 0xff : v == 0xffff) && org_c);
setPSW_v(word_mode ? (v & 0xff) == 0x80 : v == 0x8000);
setRegister(dst_reg, false, v);
if (IS_0(vo, word_mode) && org_c)
setPSW_c(true);
}
else {
uint16_t a = getGAMAddress(dst_mode, dst_reg, word_mode, false);
uint16_t v = b -> read(a, word_mode);
int32_t vl = (v - getPSW_c()) & (word_mode ? 0xff : 0xffff);
uint16_t a = getGAMAddress(dst_mode, dst_reg, word_mode, false);
const uint16_t vo = b -> read(a, word_mode);
bool org_c = getPSW_c();
uint16_t v = (vo - org_c) & (word_mode ? 0xff : 0xffff);
b->write(a, word_mode, vl);
b->write(a, word_mode, v);
setPSW_n(SIGN(vl, word_mode));
setPSW_z(IS_0(vl, word_mode));
setPSW_v(vl == 0x8000); // FIXME? v/c flags?
setPSW_n(SIGN(v, word_mode));
setPSW_z(IS_0(v, word_mode));
setPSW_v(word_mode? (v & 0xff) == 0x80 : v == 0x8000); // FIXME? v/c flags?
if (v == 0 && getPSW_c())
if (IS_0(vo, word_mode) && org_c)
setPSW_c(true);
else
setPSW_c(false);
}
break;
}