Count until compare, then re-initialize. If counting up, a successful compare occurs when the counter reaches a COMP1 value. If counting down, a successful compare occurs when the counter reaches a COMP2 value. When output mode $4 is used, alternating values of COMP1 and COMP2 are used to generate successful comparisons. For example, the counter counts until a COMP1 value is reached, re-initializes, counts until COMP2 value is reached, re-initializes, counts until COMP1 value is reached, and so on.