A mortgage securing a revolving line of credit under which advances, payments, and readvances may be made from time to time, and which states the maximum amount of the line of credit which may be secured at any one time, is effective as notice to parties from the time the mortgage is filed and registered as to all advances and readvances secured thereby, regardless of the time or amount of advances, payments, or readvances and whether or not the advances or readvances are obligatory.