The iButton®256-bit EEPROM (DS1972) is a 1024-bit, 1-Wire®EEPROM chip in a rugged iButton package. Data is written to an 8-byte scratchpad, verified, and then copied to the EEPROM memory. As a special feature, the four memory pages can individually be write protected or put in EPROM-emulation mode, where bits can only be changed from a 1 to a 0 state. The DS1972 communicates over the single-conductor 1-Wire bus. The communication follows the standard 1-Wire protocol. Each device has its own unalterable and unique 64-bit ROM registration number that is factory lasered into the device. The registration number is used to address the device in a multidrop, 1-Wire net environment.ApplicationsAccess Control/Parking MeterInventory ControlMaintenance/Inspection Data StorageTool ManagementWork-in-Progress Tracking