Datasheet

Dataiswrittentobytes4:2 of thescratchpadusingthe
Write Scratchpad [4Eh] command; the data must be
transmitted to the device starting with the least significant
bit of byte 2. To verify data integrity, the scratchpad can
be read (using the Read Scratchpad [BEh] command)
after the data is written. When reading the scratchpad,
data is transferred over the 1-Wire bus starting with the
least significant bit of byte 0. To transfer the T
H
, T
L
, and
configuration data from the scratchpad to EEPROM, the
mastermustissuetheCopyScratchpad[48h]command.
Data in the EEPROM registers is retained when the
deviceispowereddown;atpower-uptheEEPROMdata
is reloaded into the corresponding scratchpad locations.
DatacanalsobereloadedfromEEPROMtothescratch-
pad at any time using the Recall E
2
[B8h]command.The
master can issue read time slots following the Recall
E
2
command, and the device indicates the status of the
recall by transmitting 0 while the recall is in progress and
1 when the recall is done.
Conguration Register
Byte4ofthescratchpadmemorycontainstheconfigura-
tion register, which is organized as shown in Configuration
Register Format. The user can set the conversion resolu-
tion of the device using the R0 and R1 bits in this register,
as shown in Table 2. The power-up default of these bits is
R0=1andR1=1(12-bitresolution).Notethatthereis
a direct trade-off between resolution and conversion time.
Bit7andbits4:0intheconfigurationregisterarereserved
for internal use by the device and cannot be overwritten.
Conguration Register Format
Table 2. Thermometer Resolution Configuration
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0 R1 R0 1 1 1 1 1
R1 R0 RESOLUTION (BITS) MAX CONVERSION TIME
0 0 9 93.75ms (t
CONV
/8)
0 1 10 187.5ms (t
CONV
/4)
1 0 11 375ms (t
CONV
/2)
1 1 12 750ms (t
CONV
)
MAX31820PAR 1-Wire, Parasite-Power,
Ambient Temperature Sensor
www.maximintegrated.com
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