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| Both sides previous revision Previous revision Next revision | Previous revision | ||
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ff3:ff3us:doc:snes:opcode [2017/04/12 21:16] hatzen08 [BIT] |
ff3:ff3us:doc:snes:opcode [2022/09/21 18:38] (current) strotlog undo incorrect changes to c flag: c=1 carries in a 1 in adds; c=1 is set by overflowing |
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| Add or subtract the value in the A or C register with the value in the designed memory address. ADC will add the value and SBC will subtract the value. | Add or subtract the value in the A or C register with the value in the designed memory address. ADC will add the value and SBC will subtract the value. | ||
| - | When the carry flag is unset, a value of one will be added in the addition or subtraction operation. | + | When the carry flag is set, a value of one will be added in the addition or subtraction operation. |
| The operation can overflow or underflow. It is the coder responsibility to check these cases and adjust the resulting value. A common method is to check the carry flag for overflow or underflow and cap the value to a prefixed setting. | The operation can overflow or underflow. It is the coder responsibility to check these cases and adjust the resulting value. A common method is to check the carry flag for overflow or underflow and cap the value to a prefixed setting. | ||
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| ^ Opcode | ^ Opcode | ||