T5557/5567 is a contactless R/W identification IC for applications in 125KHz frequency range. The antenna and chip together form a transponder or tag. The on-chip 330-bit EEPROM (10 blocks, 33 bits each) can be read and written block-wise from a reader. Block 0 is reserved for setting the operation modes of the T5557/67 tag. Block 7 may contain password to prevent unauthorized writing. Data is transmitted from the IDIC using load modulation.