DS2704: 1280-Bit EEPROM with SHA-1 Authentication

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PIN DESCRIPTION

PIN

SYMBOL

FUNCTION

6

DQ

Serial interface data I/O pin. Bi-directional data transmit and receive at 16KBPS

or 143KBPS

5

VSS

Supply GND and reference for serial communication. Attach VSS to battery

pack negative terminal

1

VDD

Supply input. Bypass to VSS with 0.01

mF typical

2, 3, 4

NC

No Connection

Figure 1. Block Diagram

EEPROM STATUS

Data Field

1-Wire Interface

Memory Control

CRC Generator

DQ

VSS

SHA-1 Algorithm,

Constants and W0-

W15, A-E Registers

VDD

Multi-Stage

Charge Pump

64 bit ROM ID

Vpp

EEPROM Memory

Data Field

5 page x 32 byte

(1280 bit)

64 bit Secret

Dout’

Din

DETAILED DESCRIPTION

The DS2704 is comprised of an EEPROM memory array and SHA-1 Authentication function that are accessed via

a 1-Wire interface. The 1-Wire interface controls access by a host system to the 64-bit Net Address (ROM ID),

SHA-1 Authentication, 1280-bit EEPROM memory and EEPROM Status.

The DS2704 operates in one of four modes: standby, communication, computation and programming. Standby

mode is the default mode of operation. Whenever any task has been completed, the IC will automatically return to

been entered, DQ can be returned to logic high and standby mode is retained. Most operations are performed in

communication mode, with the host system addressing the DS2704 using Net Address commands and then

retrieving EEPROM and Status data using memory function commands or setting up an authentication exchange

selection of Standard or Overdrive bus timing.

current occurs after the last bit of one of the Compute MAC function commands is sent.