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fix ADC bug where V is calculated with new A instead of old A

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Vineet K 2024-06-29 09:51:12 -04:00
parent f16ab6cb6d
commit 5d36aeb885
1 changed files with 2 additions and 1 deletions
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3
cpu.c
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@ -218,11 +218,12 @@ adc(uint8_t arg)
uint16_t sum; // 16-bit sum makes it easier to determine carry flag uint16_t sum; // 16-bit sum makes it easier to determine carry flag
sum = regs.a + arg + regs.status.carry; sum = regs.a + arg + regs.status.carry;
regs.a = sum & 0xFF;
regs.status.carry = sum > 0xFF; regs.status.carry = sum > 0xFF;
/* overflow flag formula: https://stackoverflow.com/a/29224684 */ /* overflow flag formula: https://stackoverflow.com/a/29224684 */
regs.status.overflow = (~(regs.a ^ arg) & (regs.a ^ sum) & 0x80) != 0; regs.status.overflow = (~(regs.a ^ arg) & (regs.a ^ sum) & 0x80) != 0;
regs.a = sum & 0xFF;
STATUS_UPDATE_ZERO(regs.a); STATUS_UPDATE_ZERO(regs.a);
STATUS_UPDATE_NEGATIVE(regs.a); STATUS_UPDATE_NEGATIVE(regs.a);
} }