DS2417 Ver la hoja de datos (PDF) - Maxim Integrated

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DS2417

1-Wire Time Chip with Interrupt

Maxim Integrated 

DS2417

64-BIT LASERED ROM

Each DS2417 contains a unique ROM code that is 64 bits long. The first eight bits are a 1-Wire family code.

The next 48 bits are a unique serial number. The last eight bits are a CRC of the first 56 bits. (See Figure 3.)

The 1-Wire CRC is generated using a polynomial generator consisting of a shift register and XOR gates as

shown in Figure 4. The polynomial is X8 + X5 + X4 + 1. Additional information about the Dallas

Semiconductor 1-Wire Cyclic Redundancy Check is available in Application Note 27. The shift register bits

are initialized to zero. Then starting with the least significant bit of the family code, one bit at a time is

shifted in. After the 8th bit of the family code has been entered, then the serial number is entered. After the

48th bit of the serial number has been entered, the shift register contains the CRC value. Shifting in the eight

bits of CRC should return the shift register to all zeros. The 64-bit ROM and ROM Function Control section

allow the DS2417 to operate as a 1-Wire device and follow the 1-Wire protocol detailed in the section "1-

Wire Bus System".

HIERARCHICAL STRUCTURE FOR 1-WIRE PROTOCOL Figure 2

Bus

Master

1-Wire Bus

Other

Devices

Command

Level

1-Wire ROM Function

Commands (see Figure 7)

DS2417

Available

Commands

Read ROM

Match ROM

Search ROM

Skip ROM

Data Fields

Affected

64-bit ROM

64-bit ROM

64-bit ROM

N/A

DS2417 specific

Function Commands

(see Figure 5)

Write Clock

Read Clock

RTC Counter, Device Control

RTC Counter, Device Control

64-BIT LASERED ROM Figure 3

MSB

8-Bit CRC Code

MSB

LSB MSB

48-Bit Serial Number

LSB

8-Bit Family Code (27h)

LSB MSB

LSB

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