DS1822

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issued the master must enable a strong pullup on the 1-Wire bus for at least 10ms as described in the

POWERING THE DS1822 section.

RECALL E

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

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

and configuration registers).

4Eh

Master transmits 3 data bytes to

DS1822.

3

Copy Scratchpad

configuration register data

from the scratchpad to

EEPROM.

48h

None

1

Recall E

2

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.