AT24C20PU27 AT24C21 AT24C21 SC2.5 AT24C21 SC2.5 AT24C21-10PC-2.5 AT24C21-10PI-2.5 AT24C21-10SC-2.5 AT24C21-10SC-2.7 AT24C21-10SI-2.5 AT24C21-10SI-2.7