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System Specification for C65Fred BowenMarch 1, 1991 65CE02 Instruction Set

Add memory to accumulator with carry   ADC


Addressing ModeAbbrev.Opcode
immediate IMM 69
base page BP 65
base page indexed X BP,X 75
absolute ABS 6D
absolute indexed X ABS,X 7D
absolute indexed Y ABS,Y 79
base page indexed indirect X (BP,X) 61
base page indirect indexed Y (BP),Y 71
base page indirect indexed Z (BP),Z 72

Bytes Cycles Mode
23base page non-indexed, or indexed X or Y
34absolute non-indexed, or indexed X or Y
25base page indexed indirect X, or indirect indexed Y or Z

The ADC instructions add data fetched from memory and carry to the contents of the accumulator. The results of the add are then stored in the accumulator. If the "D" or Decimal Mode flag, in the processor status register, then a Binary Coded Decimal (BCD) add is performed.

The "N" or Negative flag will be set if the sum is negative, otherwise it is cleared. The "V" or Overflow flag will be set if the sign of the sum is different from the sign of both addends, indicating a signed overflow. Otherwise, it is cleared. The "Z" or Zero flag is set if the sum (stored into the accumulator) is zero, otherwise, it is cleared. The "C" or carry is set if the sum of the unsigned addends exceeds 255 (binary mode) or 99 (decimal mode).

  N V E B D I Z C
  N V - - - - Z C

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