DS28E01-100 データシートの表示（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS28E01-100

1K-Bit Protected 1-Wire EEPROM with SHA-1 Engine

Dallas Semiconductor -> Maxim Integrated 

Abridged Data Sheet

DS28E01-100

MEMORY AND SHA FUNCTION COMMANDS

This section describes the commands and flow charts to use the memory and SHA-1 engine of the device. It

includes Tables 1 to 4 and Figure 8. Please refer to the full version of the data sheet.

SHA-1 COMPUTATION ALGORITHM

This description of the SHA computation is adapted from the Secure Hash Standard SHA-1 document that can be

downloaded from the NIST website (www.itl.nist.gov/fipspubs/fip180-1.htm). Further details are found in the full

version of the data sheet.

1-Wire BUS SYSTEM

The 1-Wire bus is a system that has a single bus master and one or more slaves. In all instances the DS28E01-

100 is a slave device. The bus master is typically a microcontroller. The discussion of this bus system is broken

down into three topics: hardware configuration, transaction sequence, and 1-Wire signaling (signal types and

timing). The 1-Wire protocol defines bus transactions in terms of the bus state during specific time slots, which are

initiated on the falling edge of sync pulses from the bus master.

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 tri-state

outputs. The 1-Wire port of the DS28E01-100 is open drain with an internal circuit equivalent to that shown in

Figure 9.

A multidrop bus consists of a 1-Wire bus with multiple slaves attached. The DS28E01-100 supports both a Stan-

dard and Overdrive communication speed of 15.3kbps (max) and 125kbps (max), respectively. Note that legacy 1-

Wire products support a standard communication speed of 16.3kbps and Overdrive of 142kbps. The slightly

reduced rates for the DS28E01-100 are a result of additional recovery times, which in turn were driven by a 1-Wire

physical interface enhancement to improve noise immunity. The value of the pullup resistor primarily depends on

the network size and load conditions. The DS28E01-100 requires a pullup resistor of 2.2kΩ (max) at any speed.

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 16µs

(Overdrive speed) or more than 120µs (standard speed), one or more devices on the bus may be reset.

Figure 9. Hardware Configuration

BUS MASTER

RX

VPUP

RPUP

DS28E01 1-Wire PORT

DATA

RX

TX

RX = RECEIVE

Open Drain

Port Pin

TX = TRANSMIT

IL

TX

100 Ω

MOSFET

8 of 16

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