DS28EA00 1-Wire Digital Thermometer with Sequence Detect and PIO

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64-BIT REGISTRATION NUMBER

Each DS28EA00 contains a unique Registration Number that is 64 bits long. The first 8 bits are a 1-Wire family

code. The next 48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. See Figure 3 for

details. 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 X

Redundancy Check (CRC) is available in Application Note 27.

The shift register bits are initialized to 0. 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 48-bit serial number is entered.

After the last byte of the serial number has been entered, the shift register contains the CRC value. Shifting in the 8

bits of CRC returns the shift register to all 0s.

Figure 2. Hierachical Structure for 1-Wire Protocol

DS28EA00

Available

Commands:

Command

Level:

Data Field

Affected:

1-Wire ROM Function

Commands (see Figure 12)

Read ROM

Match ROM

Search ROM

Conditional Search

ROM

Conditional Read

ROM

Skip ROM

Overdrive Skip

Overdrive Match

64-bit Reg. #

64-bit Reg. #

64-bit Reg. #

64-bit Reg. #, Temperature Alarm

Registers, Scratchpad

64-bit Reg. #, PIOB pin state, Chain

state

(none)

64-bit Reg. #, OD-Flag

64-bit Reg. #, OD-Flag

Device-Specific

Control Function

Commands (see Figure 10)

Write Scratchpad

Read Scratchpad

Copy Scratchpad

Convert Temperature

Read Power Mode

Recall EEPROM

PIO Access Read

PIO Access Write

Chain

Scratchpad

Scratchpad

Temperature Alarm and Configuration

Registers

Scratchpad, Temperature Alarm

Registers

Scratchpad, Temperature Alarm and

Configuration Registers

PIO pins

PIO pins

Chain state, PIOA pin state

Figure 3. 64-Bit Registration Number

MSB

LSB

8-Bit

CRC Code

48-Bit Serial Number

8-Bit Family

Code (42h)

MSB

LSB

MSB

LSB

MSB

LSB