DS2703 Dallas Semiconductor, DS2703 Datasheet - Page 12

• Manufacturer Part Number: DS2703
• Description: SHA-1 Battery Pack Authentication IC
• Manufacturer: Dallas Semiconductor

DS2703 SHA-1 Battery Pack Authentication IC
NET ADDRESS COMMANDS
Once the bus master has detected the presence of one or more slaves, it can issue one of the net address
commands described in the following paragraphs. The name of each Net Address command (ROM command) is
followed by the 8-bit opcode for that command in square brackets. Figure 6 presents a transaction flowchart of the
net address commands.
Read Net Address [33h]. This command allows the bus master to read the DS2703’s 1-Wire net address. This
command can only be used if there is a single slave on the bus. If more than one slave is present, a data collision
occurs when all slaves try to transmit at the same time (open drain produces a wired-AND result).
Match Net Address [55h]. This command allows the bus master to specifically address one DS2703 on the 1-Wire
bus. Only the addressed DS2703 responds to any subsequent function command. All other slave devices ignore
the function command and wait for a reset pulse. This command can be used with one or more slave devices on
the bus.
Skip Net Address [CCh]. This command saves time when there is only one DS2703 on the bus by allowing the
bus master to issue a function command without specifying the address of the slave. If more than one slave device
is present on the bus, a subsequent function command can cause a data collision when all slaves transmit data at
the same time.
Search Net Address [F0h]. This command allows the bus master to use a process of elimination to identify the
1-Wire net addresses of all slave devices on the bus. The search process involves the repetition of a simple three-
step routine: read a bit, read the complement of the bit, then write the desired value of that bit. The bus master
performs this simple three-step routine on each bit location of the net address. After one complete pass through all
64 bits, the bus master knows the address of one device. The remaining devices can then be identified on
®
additional iterations of the process. See Chapter 5 of the Book of DS19xx iButton
Standards for a comprehensive
discussion of a net address search, including an actual example (www.maxim-ic.com/iButtonBook).
iButton is a registered trademark of Dallas Semiconductor.
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