BVC (short for "Branch if oVerflow Clear") is the mnemonic for a machine language instruction which branches, or "jumps", to the address specified if, and only if the overflow flag is clear. If the overflow flag is set when the CPU encounters a BVC instruction, the CPU will continue at the instruction following the BVC rather than taking the jump.
Addressing mode[edit | edit source]
BVC only supports the Relative addressing mode, as shown in the table at right.
In the assembler formats listed, nn is a one-byte (8-bit) relative address. The relative address is treated as a signed byte; that is, it shifts program execution to a location within a number of bytes ranging from -128 to 127, relative to the address of the instruction following the branch instruction.
The execution time for BVC is not a fixed value, but depends on the circumstances. The listed time is valid only in cases where BVC does not take the branch. If it does take the branch, execution takes one additional clock cycle. Furthermore, if the branching crosses a page boundary, yet another cycle must be added to the execution time listed.
CPU flags[edit | edit source]
BVC does not affect any of the CPU's status flags.