Rainbow Electronics DS18B20 - Manual (Page 11)

DS18B20
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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 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. Refer to the POWERING THE
DS18B20 section for usage information for this command.
DS18B20 FUNCTION COMMAND SET Table 4
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 configuration registers).
4Eh Master transmits 3 data bytes to
DS18B20. 3
Copy Scratchpad Copies T
H
, T
L
, and
configuration register data
from the scratchpad to
EEPROM.
48h None 1
Recall E
2
Recalls T
H
, T
L
, 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.
NOTES:
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.
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.