DS2432X データシートの表示（PDF） - Maxim Integrated

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DS2432X

1Kb Protected 1-Wire EEPROM with SHA-1 Engine

Maxim Integrated 

ABRIDGED DATA SHEET

DS2432

HARDWARE CONFIGURATION

The 1-Wire bus has only a single line by definition; it is important that each device on the bus be able to

drive it at the appropriate time. To facilitate this, each device attached to the 1-Wire bus must have open

drain or 3-state outputs. The 1-Wire port of the DS2432 is open drain with an internal circuit equivalent

to that shown in Figure 8. A multidrop bus consists of a 1-Wire bus with multiple slaves attached. At

regular speed the 1-Wire bus has a maximum data rate of 15.3kbps. The speed can be boosted to 125kbps

by activating the Overdrive Mode. The DS2432 requires a 1-Wire pullup resistor of maximum 2.2 kΩ for

executing any of its memory and SHA-1 function commands at any speed. When communicating with

several DS2432 simultaneously, e.g., to install the same secret in several devices, the resistor should be

bypassed by a low-impedance pullup to VPUP while the device transfers data from the scratchpad to the

EEPROM.

The idle state for the 1-Wire bus is high. If for any reason a transaction needs to be suspended, the bus

MUST be left in the idle state if the transaction is to resume. If this does not occur and the bus is left low

for more than 16 µs (Overdrive Speed) or more than 120 µs (regular speed), one or more devices on the

bus may be reset.

HARDWARE CONFIGURATION Figure 8

BUS MASTER

VPUP

DS2432 1-Wire PORT

RPUP

RX

DATA

RX

TX

RX = RECEIVE

Open Drain

Port Pin

TX = TRANSMIT

IL

TX

100 Ω

MOSFET

TRANSACTION SEQUENCE

The protocol for accessing the DS2432 via the 1-Wire port is as follows:

• Initialization

• ROM Function Command

• Memory or SHA-1 Function Command

• Transaction/Data

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.

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