DS18B20

7 of 22

MEMORY

The DS18B20’s memory is organized as shown in Figure 7. The memory consists of an SRAM

can serve as general-purpose memory. All memory commands are described in detail in the DS18B20

Function Commands section.

Byte 0 and byte 1 of the scratchpad contain the LSB and the MSB of the temperature register,

contains the configuration register data, which is explained in detail in the Configuration Register section.

Bytes 5, 6, and 7 are reserved for internal use by the device and cannot be overwritten.

Byte 8 of the scratchpad is read-only and contains the CRC code for bytes 0 through 7 of the scratchpad.

The DS18B20 generates this CRC using the method described in the CRC Generation section.

Data is written to bytes 2, 3, and 4 of the scratchpad using the Write Scratchpad [4Eh] command; the data

must be transmitted to the DS18B20 starting with the least significant bit of byte 2. To verify data

integrity, the scratchpad can be read (using the Read Scratchpad [BEh] command) after the data is

written. When reading the scratchpad, data is transferred over the 1-Wire bus starting with the least

the master must issue the Copy Scratchpad [48h] command.

Data in the EEPROM registers is retained when the device is powered down; at power-up the EEPROM

data is reloaded into the corresponding scratchpad locations. Data can also be reloaded from EEPROM to

the scratchpad at any time using the Recall E

2

[B8h] command. The master can issue read time slots

following the Recall E

while the recall is in progress and 1 when the recall is done.

Figure 7. DS18B20 Memory Map

SCRATCHPAD

Byte 0

Temperature LSB (50h)

Byte 1

Temperature MSB (05h)

EEPROM

Byte 2

Byte 3

Byte 4

Configuration Register*

Configuration Register

Byte 5

Reserved (FFh)

Byte 6

Reserved

Byte 7

Reserved (10h)

Byte 8

CRC*

(85°C)