iButton DESCRIPTION
The DS1920 Temperature  iButton provides 9-bit temperature readings which indicate the temperature of the device. Information is sent to/from the DS1920 over a 1-Wire interface. Power for reading, writing, and performing temperature conversions is derived from the data line itself. Because each DS1920 contains a unique silicon serial number, multiple DS1920s can exist on the same 1-Wire bus. This allows for placing temperature sensors in many different places. Applications where this feature is useful include HVAC environmental controls, sensing temperatures inside buildings, equipment or machinery, and in process monitoring and control.

SPECIAL FEATURES
Digital thermometer measures temperatures from -55°C to +100°C in typically 0.2 seconds
Zero standby power
0.5°C resolution, digital temperature reading is two’ s complement of °C value
Access to internal counters allows increased resolution through interpolation
Reduces control, address, data, and power to a single data contact
8-bit device-generated CRC for data integrity
8-bit family code specifies DS1920 communications requirements to reader
Special command set allows user to skip ROM section and do temperature measurements simultaneously for all devices on the bus
2 bytes of EEPROM to be used either as alarm triggers or user memory
Alarm search directly indicates which device senses alarming temperatures