DS18B20
COPY SCRATCHPAD [48h]
This command copies the contents of the scratchpad T
H
, T
L
and configuration registers (bytes 2, 3 and 4)
to EEPROM. If the device is being used in parasite power mode, within 10µs (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 (T
H
and T
L
) 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
1-Wire BUS
COMMAND
DESCRIPTION
PROTOCOL
ACTIVITYAFTER
COMMAND IS ISSUED
TEMPERATURE CONVERSION COMMANDS
Convert T
Initiates temperature
DS18B20 transmits
conversion.
conversion status to master
44h
(not applicable for parasite-
powered DS18B20s).
MEMORY COMMANDS
Read
Reads the entire scratchpad
DS18B20 transmits up to 9
BEh
Scratchpad
including the CRC byte.
data bytes to master.
Write
Writes data into scratchpad
Master transmits 3 data bytes
Scratchpad
bytes 2, 3, and 4 (T
H
, T
L
,
to DS18B20.
4Eh
and configuration
registers).
Copy
Copies T
H
, T
L
, and
None
Scratchpad
configuration register data
48h
from the scratchpad to
EEPROM.
2
Recalls T
H
, T
L
, and
DS18B20 transmits recall
Recall E
configuration register data
status to master.
B8h
from EEPROM to the
scratchpad.
Read Power
Signals DS18B20 power
DS18B20 transmits supply
B4h
Supply
supply mode to the master.
status to master.
Note 1:
Note 2:
Note 3:
NOTES
1
2
3
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.
The master can interrupt the transmission of data at any time by issuing a reset.
All three bytes must be written before a reset is issued.
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