Rainbow Electronics DS1822 - Manual (Page 11)

DS1822
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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 DS1822 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 DS1822 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 DS1822s on the
bus are using parasite power. During the read time slot, parasite powered DS1822s will pull the bus low,
and externally powered DS1822s will let the bus remain high. Refer to the POWERING THE DS1822
section for usage information for this command.
DS1822 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 DS1822 transmits conversion
status to master (not applicable
for parasite-powered DS1822s). 1
MEMORY COMMANDS
Read Scratchpad Reads the entire scratchpad
including the CRC byte.
BEh DS1822 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
DS1822. 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 DS1822 transmits recall status to
master.
Read Power
Supply Signals DS1822 power
supply mode to the master. B4h DS1822 transmits supply status
to master.
NOTES:
1. For parasite-powered DS1822s, 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.