DS2432X Dallas Semiconducotr, DS2432X Datasheet - Page 21

• Manufacturer Part Number: DS2432X
• Description: 1k-Bit Protected 1-Wire EEPROM with SHA-1 Engine
• Manufacturer: Dallas Semiconducotr

PRELIMINARY
HARDWARE CONFIGURATION Figure 8
TRANSACTION SEQUENCE
The protocol for accessing the DS2432 via the 1-Wire port is as follows:
INITIALIZATION
All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence
consists of a reset pulse transmitted by the bus master followed by presence pulse(s) transmitted by the
slave(s). The presence pulse lets the bus master know that the DS2432 is on the bus and is ready to
operate. For more details, see the “1-Wire Signaling” section.
ROM FUNCTION COMMANDS
Once the bus master has detected a presence, it can issue one of the seven ROM function commands that
the DS2432 supports. All ROM function commands are eight bits long. A list of these commands follows
(refer to flowchart in Figure 9):
Read ROM [33h]
This command allows the bus master to read the DS2432’s 8-bit family code, unique 48-bit serial
number, and 8-bit CRC. This command should only be used if there is a single slave on the bus. If more
than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same
time (open drain will produce a wired-AND result). The resultant family code and 48-bit serial number
read by the master will be invalid.
Match ROM [55h]
The match ROM command, followed by a 64-bit registration number, allows the bus master to address a
specific DS2432 on a multidrop bus. Only the DS2432 that exactly matches the 64-bit registration
number will respond to the following memory function command. All other slaves will wait for a reset
pulse. This command can be used with a single or multiple devices on the bus.
Initialization
ROM Function Command
Memory or SHA Function Command
Transaction/Data
RX
TX
BUS MASTER
Open Drain
Port Pin
V
R
PUP
RX = RECEIVE
TX = TRANSMIT
PU
21 of 30
5 µA
Typ.
DATA
DS2432 1-Wire PORT
100
MOSFET
RX
TX
DS2432