A <- A - n - CY
The n integer along with the Carry Flag (C in the F Register) is subtracted from the contents of the Accumulator, and the results are stored in the Accumulator.
|S||is set if result is negative, otherwise it is reset.|
|Z||is set if result is 0, otherwise it is reset.|
|H||is set if borrow from bit 4, otherwise it is reset.|
|P/V||is set if overflow, otherwise it is reset|
|C||is set if borrow, otherwise it is reset.|
If the Accumulator contains $23 and the Carry Flag is set then upon the execution of
the Accumulator contains $12.