Datasheet

DS18S20
16 of 23
Figure 14. ROM Commands Flowchart
CCh
SKIP ROM
COMMAND
MASTER T
X
RESET PULSE
DS18S20 T
X
PRESENCE
PULSE
MASTER T
X
ROM
COMMAND
33h
READ ROM
COMMAND
55h
MATCH ROM
COMMAND
F0h
SEARCH ROM
COMMAND
ECh
ALARM SEARCH
COMMAND
MASTER T
X
BIT 0
DS18S20 T
X
BIT 0
DS18S20 T
X
BIT 0
MASTER T
X
BIT 0
BIT 0
MATCH?
MASTER T
X
BIT 1
BIT 1
MATCH?
BIT 63
MATCH?
MASTER T
X
BIT 63
N
Y
Y Y Y
Y
N
N
N
N
N
N
N
Y
Y
Y
DS18S20 T
X
BIT 1
DS18S20 T
X
BIT 1
MASTER T
X
BIT 1
DS18S20 T
X
BIT 63
DS18S20 T
X
BIT 63
MASTER T
X
BIT 63
BIT 0
MATCH?
BIT 1
MATCH?
BIT 63
MATCH?
N
N
N
Y
Y
Y
DS18S20 T
X
FAMILY CODE
1 BYTE
DS18S20 T
X
SERIAL NUMBER
6 BYTES
DS18S20 T
X
CRC BYTE
DS18S20 T
X
BIT 0
DS18S20 T
X
BIT 0
MASTER T
X
BIT 0
N
Y
DEVICE(S)
WITH ALARM
FLAG SET?
Initialization
Sequence
MASTER T
X
FUNCTION
COMMAND
(FIGURE 15)