Datasheet

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, para-
site powered DS18B20s will pull the bus low, and exter-
nally 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
Note 1: For parasite-powered DS18B20s, the master must enable a strong pullup on the 1-Wire bus during temperature conver-
sions 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.
COMMAND DESCRIPTION PROTOCOL
1-Wire BUS ACTIVITY AFTER
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 (T
H
, T
L
, and conguration registers).
4Eh
Master transmits 3 data bytes to
DS18B20.
3
Copy
Scratchpad
Copies T
H
, T
L
, and conguration register
data from the scratchpad to EEPROM.
48h None 1
Recall E
2
Recalls T
H
, T
L
, and conguration 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.
DS18B20 Programmable Resolution
1-Wire Digital Thermometer
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