Datasheet

MAX31850/MAX31851
Cold-Junction Compensated, 1-Wire
Thermocouple-to-Digital Converters
22Maxim Integrated
Operation Example
Table 6 shows an operation example in which there are
multiple devices on the bus using parasite power. The
bus master initiates a temperature conversion in a spe-
cific MAX31850/MAX31851 and then reads Scratchpad
and recalculates the CRC to verify the data.
Figure 13. Recommended Master Read-One Timing
Table 6. Operation Example
MASTER
MODE
DATA (LSB FIRST) COMMENTS
Tx Reset Master issues reset pulse.
Rx Presence Devices respond with presence pulse.
Tx F0h Master issues Search ROM command
Tx Reset Master issues reset pulse.
Rx Presence Devices respond with presence pulse.
Tx 55h Master issues Match ROM command for desired address
Tx 64-bit ROM code Master sends device ROM code.
Tx 44h Master issues Convert T command.
Tx
DQ line held high by
strong pullup
Master applies strong pullup to DQ for the duration of the conversion (t
CONV
).
Tx Reset Master issues reset pulse.
Rx Presence Devices respond with presence pulse.
Tx 55h Master issues Match ROM command.
Tx 64-bit ROM code Master sends device ROM code.
Tx BEh Master issues Read Scratchpad command.
Rx 9 data bytes
Master reads entire scratchpad including CRC. The master then recalculates the CRC of the
first 8 data bytes from the scratchpad and compares the calculated CRC with the read CRC
(byte 9). If they match, the master continues; if not, the read operation is repeated.
V
PU
V
IH
OF MASTER
t
INIT
=
SMALL
t
RC
=
SMALL
MASTER SAMPLES
15µs
1-Wire BUS
GND
BUS MASTER PULLING LOW RESISTOR PULLUP