DS18B20X
is issued the master must enable a strong pullup on the 1-wire bus for at least 10 ms as described in the
POWERING THE DS18B20X 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 DS18B20X 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 DS18B20Xs on
the bus are using parasite power. During the read time slot, parasite powered DS18B20Xs will pull the
bus low, and externally powered DS18B20Xs will let the bus remain high. Refer to the POWERING
THE DS18B20X section for usage information for this command.
DS18B20X FUNCTION COMMAND SET
Table 4
1-Wire Bus Activity
Command
Description
Protocol
After Command is Issued
TEMPERATURE CONVERSION COMMANDS
Convert T
Initiates temperature
44h
DS18B20X transmits conversion
conversion.
status to master (not applicable
for parasite-powered
DS18B20Xs).
MEMORY COMMANDS
Read Scratchpad Reads the entire scratchpad
BEh
DS18B20X transmits up to 9
including the CRC byte.
data bytes to master.
Write Scratchpad Writes data into scratchpad
4Eh
Master transmits 3 data bytes to
bytes 2, 3, and 4 (T
H
, T
L
,
DS18B20X.
and configuration registers).
Copy Scratchpad Copies T
H
, T
L
, and
48h
None
configuration register data
from the scratchpad to
EEPROM.
2
Recalls T
H
, T
L
, and
B8h
DS18B20X transmits recall
Recall E
configuration register data
status to master.
from EEPROM to the
scratchpad.
Read Power
Signals DS18B20X power
B4h
DS18B20X transmits supply
Supply
supply mode to the master.
status to master.
Notes
1
2
3
1
NOTES:
1. For parasite-powered DS18B20Xs, 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.
2. The master can interrupt the transmission of data at any time by issuing a reset.
3. All three bytes must be written before a reset is issued.
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DALLAS [ DALLAS SEMICONDUCTOR ]
