ATMEL ATA5577 Card
The ATA5577 is a contactless read/write identification IC (IDIC®) for software at the 125-kHz or 134-kHz frequency group. A single coil on the processor functions as the IC’s electricity source and bi-directional communication port. The antenna and processor collectively form a transponder or tag.
The on-chip 363-bit EEPROM (11 cubes with 33 pieces each) could be written and read block-wise in the base station (reader).
Data is sent by the IDIC (uplink) utilizing load modulation. This is accomplished by damping the RF field using a resistive load between the 2 terminals Coil 1 plus Coil 2. The IC receives and decodes sequential base station controls (downlink), which can be analyzed as 100% amplitude modulated (OOK) pulse-interval-encoded little streams.