Hardware manual

Microcomputer Technical Q&A

Q&A No.: QAH8S-002

Category: CPU

Subject: Difference between V Flag and C Flag in CCR

Question

The V flag and C flag in CCR are both set if overflow occurs during an operation. What is the

difference between these flags?

Answer

The V flag in CCR is used to identify whether overflow occurs in a signed operation. To take the

example of a byte-size operation, this flag is set to 1 if the operation result is smaller than the

negative minimum value (H'80) larger than the positive maximum value (H'7F).

V flag

H'80

H'7FH'00

Overflow Overflow

The C flag, on the other hand, is used to identify whether overflow occurs in an unsigned

operation. To take the example of a byte-size operation, this flag is set to 1 if the operation result

is larger than the maximum value (H'FF) or smaller than the minimum value (H'00).

C flag

H'00

H'FF

Overflow Overflow