1.11.1 MCU ALU Status Bits

The MCU operation Status bits are either affected or used by the majority of instructions in the instruction set. Most of the logic, math, rotate/shift and bit instructions modify the MCU Status bits after execution, and the conditional branch instructions use the state of individual Status bits to determine the flow of program execution. All conditional branch instructions are listed in Conditional Branch Instructions.

The Carry (C), Zero (Z), Overflow (OV) and Negative (N) bits show the immediate status of the MCU ALU by indicating whether an operation has resulted in a Carry, Zero, Overflow or Negative result. When a subtract operation is performed, the C flag is used as a Borrow flag.

The Z Status bit is useful for extended precision arithmetic. The Z Status bit functions like a normal Z flag for all instructions except those that use a carry or borrow input (ADDC, CPB, SUBB and SUBBR). See Z Status Bit for more detailed information.