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 E2 [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 E2 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
Convert T
Description
TEMPERATURE CONVERSION COMMANDS
Initiates temperature 44h DS18B20X transmits conversion
conversion.
Protocol
After Command is Issued
Notes
1
status to master (not applicable
for parasite-powered
DS18B20Xs).
MEMORY COMMANDS
Read Scratchpad Reads the entire scratchpad
including the CRC byte.
Write Scratchpad Writes data into scratchpad
bytes 2, 3, and 4 (TH, TL,
BEh
DS18B20X transmits up to 9
data bytes to master.
Master transmits 3 data bytes to
DS18B20X.
2
3
4Eh
and configuration registers).
Copy Scratchpad Copies TH, TL, and
configuration register data
48h
B8h
B4h
None
1
from the scratchpad to
EEPROM.
Recalls TH, TL, and
Recall E2
DS18B20X transmits recall
status to master.
configuration register data
from EEPROM to the
scratchpad.
Read Power
Supply
Signals DS18B20X power
supply mode to the master.
DS18B20X transmits supply
status to master.
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 ]
