Datasheet

Figure 17. DS18S20 Function Commands Flowchart
MASTER Tx
FUNCTION
COMMAND
Y
N
44h
CONVERT
TEMPERATURE
?
DS18S20 BEGINS
CONVERSION
DEVICE
CONVERTING
TEMPERATURE
?
N
Y
MASTER
Rx “0s”
MASTER
Rx “1
s”
MASTER ENABLES
STRONG PULLUP ON DQ
DS18S20 CONVERTS
TEMPERATURE
MASTER DISABLES
STRONG PULLUP
Y
N
48
h
COPY
SCRATCHPAD
?
PARASITE
POWER
?
N
MASTER ENABLES
STRONG PULL- UP ON DQ
DATA COPIED FROM
SCRATCHPAD TO EEPROM
MASTER DISABLES
STRONG PULLUP
MASTER
Rx “0s”
COPY IN
PROGRESS
?
Y
MASTER
Rx “1s”
RETURN TO INITIALIZATION SEQUENCE
(FIGURE 16) FOR NEXT TRANSACTION
B4h READ
POWER SUPPLY
?
Y
N
PARASITE
POWERED
?
MASTER
Rx “1s”
MASTER
Rx “0s”
MASTER Tx T
H
BYTE
TO SCRATCHPAD
Y
4Eh
WRITE
SCRATCHPAD
?
MASTER Tx T
L
BYTE
TO SCRATCHPAD
Y
N
Y
BEh
READ
SCRATCH PAD
?
HAVE 8 BYTES
BEEN READ
?
N
MASTER
Tx RESET
?
MASTER Rx DATA BYTE
FROM SCRATCHPAD
N
Y
MASTER Rx SCRATCHPAD
CRC BYTE
MASTER
Rx “1s”
Y
N
B8h
RECALL E
2
?
MASTER BEGINS DATA
RECALL FROM E
2
PROM
DEVICE
BUSY RECALLING
DATA
?
N
Y
MASTER
Rx “0s”
PARASITE
POWER
?
Y Y
N
Y
N
N
N
DS18S20 High-Precision 1-Wire Digital Thermometer
www.maximintegrated.com
Maxim Integrated │ 17