DS1921H/Z
ROM FUNCTIONS FLOW CHART Figure 13-1
Master TX
Reset Pulse
From Memory Functions
Flow Chart (Figure 10)
From Figure 13
2nd Part
N
Short
Reset Pulse?
OD = 0
Y
DS1921 TX
Presence Pulse
2)
1)
Master TX ROM
Function Command
To Figure 13
2
nd Part
33H
Read
ROM?
55H
Match
ROM?
F0H
Search
ROM?
ECH
Cond. Search
ROM?
N
N
N
N
Y
Y
Y
Y
N
N
N
Cond. Met?
Y
DS1921 TX
Family Code
1 Byte
1)
1)
1)
1)
1)
1)
1)
DS1921 TX Bit 0
DS1921 TX Bit 0
Master TX Bit 0
DS1921 TX Bit 0
DS1921 TX Bit 0
Master TX Bit 0
1)
Master TX Bit 0
N
N
Bit 0 Match?
Y
Bit 0 Match?
Bit 0 Match?
Y
DS1921 TX Bit 1
DS1921 TX Bit 1
Master TX Bit 1
Y
DS1921 TX Bit 1
DS1921 TX Bit 1
Master TX Bit 1
DS1921 TX
Temp. Range
Code and
1)
1)
1)
1)
1)
1)
1)
1)
N
Master TX Bit 1
Serial Number
6 Bytes
N
Bit 1 Match?
Y
Bit 1 Match?
Y
Bit 1 Match?
Y
DS1921 TX
CRC Byte
1)
DS1921 TX Bit 63 1)
DS1921 TX Bit 63 1)
Master TX Bit 63 1)
DS1921 TX Bit 63 1)
DS1921 TX Bit 63 1)
Master TX Bit 63 1)
1)
N
Master TX Bit 63
N
N
Bit 63 Match?
Y
Bit 63 Match?
Y
Bit 63 Match?
Y
To Figure 13
nd Part
2
From Figure 13
nd Part
1) To be transmitted or received at Overdrive speed if
OD = 1.
2) The Presence Pulse will be short if OD = 1.
To Memory Functions
Flow Chart (Figure 10)
2
27 of 44
DALLAS [ DALLAS SEMICONDUCTOR ]
