DS18B20

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COPY SCRATCHPAD [48h]

This command copies the contents of the scratchpad TH, TL and configuration registers (bytes 2, 3 and 4)

to EEPROM. If the device is being used in parasite power mode, within 10

µs (max) after this command is

issued the master must enable a strong pullup on the 1-Wire bus for at least 10ms as described in the

Powering the DS18B20 section.

RECALL E

2 [B8h]

This command recalls the alarm trigger values (TH and TL) and configuration data from EEPROM and

places the data in bytes 2, 3, and 4, respectively, in the scratchpad memory. The master device can issue

read time slots following the Recall E

2 command and the DS18B20 will indicate the status of the recall by

transmitting 0 while the recall is in progress and 1 when the recall is done. The recall operation happens

automatically at power-up, so valid data is available in the scratchpad as soon as power is applied to the

device.

READ POWER SUPPLY [B4h]

The master device issues this command followed by a read time slot to determine if any DS18B20s on the

bus are using parasite power. During the read time slot, parasite powered DS18B20s will pull the bus

low, and externally powered DS18B20s will let the bus remain high. See the Powering the DS18B20

section for usage information for this command.

Table 3. DS18B20 Function Command Set

COMMAND

DESCRIPTION

PROTOCOL

1-Wire BUS

ACTIVITYAFTER

COMMAND IS ISSUED

NOTES

TEMPERATURE CONVERSION COMMANDS

Convert T

Initiates temperature

conversion.

44h

DS18B20 transmits

conversion status to master

(not applicable for parasite-

powered DS18B20s).

1

MEMORY COMMANDS

Read

Scratchpad

Reads the entire scratchpad

including the CRC byte.

BEh

DS18B20 transmits up to 9

data bytes to master.

2

Write

Scratchpad

Writes data into scratchpad

bytes 2, 3, and 4 (TH, TL,

and configuration

registers).

4Eh

Master transmits 3 data bytes

to DS18B20.

3

Copy

Scratchpad

Copies TH, TL, and

configuration register data

from the scratchpad to

EEPROM.

48h

None

1

Recall E

2

Recalls TH, TL, and

configuration register data

from EEPROM to the

scratchpad.

B8h

DS18B20 transmits recall

status to master.

Read Power

Supply

Signals DS18B20 power

supply mode to the master.

B4h

DS18B20 transmits supply

status to master.

Note 1:

For parasite-powered DS18B20s, the master must enable a strong pullup on the 1-Wire bus during temperature

conversions and copies from the scratchpad to EEPROM. No other bus activity may take place during this time.

Note 2:

The master can interrupt the transmission of data at any time by issuing a reset.

Note 3:

All three bytes must be written before a reset is issued.