28-05-2014, 04:57 PM
A Seminar Report on 1-Wire Protocol
1-Wire Protocol.pdf (Size: 442.24 KB / Downloads: 36)
What is 1-Wire Protocol?
Basically, 1-Wire Protocol was designed Dallas Semiconductor, an associated
unit by Maxim Integrated Corp few years back.
It is a protocol to digitally communicate over twisted-pair cable with 1-
Wire components over a 1-Wire network.
1-Wire Network is defined with an open-drain (wired-AND) master/slave
multidrop architecture with resistor pull-up to a nominal 5V supply at
the master.
1-Wire network’s three components are:
A bus master with controlling software (e.g. TMEX iButton viewer)
1-Wire devices
Wiring and associated connectors
Features/Benefits
Each 1-Wire slave has stored in ROM a unique 64-bit serial number that
acts as its node address device to be individually selected from among
many that can be connected to the same bus wire.
o This globally unique address is composed of 8 bytes divided into
three main sections.
o Starting from LSB, the first byte stores the 8-bit family codes that
identify the device type.
o The next six bytes store a customizable 48-bit individual address.
o The last byte, the MSB, contains the CRC with a value based on
the data contained in the first seven bytes.
This allows master to determine if an address was read without
error. With a 248 serial number pool, conflicting or duplicate node
addresses on the network are never a problem.
1-Wire devices can be formatted with a file directory like a flopy disk –
files can be randomly accessed and changed without disturbing other
records.
Maximum data security can be provided by 1-Wire chip implementation
of the US government-certified Secure Hash Algorithm (SHA-1).
This protocol uses a single wire + ground to accomplish both
communication and power transmission as shown below.