An integer value in the specified range that is used
to index into the table. The size of the table is
fixed at 8. Each entry identifies a particular
reading of the clock filter variables in the shift
register.
Entries are added starting at index 1. The index
wraps back to 1 when it reaches 8. When the index
wraps back, the new entries will overwrite the old
entries effectively deleting the old entry.