Datasheet

DS1921G
Thermochron iButton
______________________________________________________________________________________ 29
DS1921G Tx
PRESENCE PULSE
MASTER Tx
RESET PULSE
MASTER Tx ROM
FUNCTION COMMAND
DS1921G Tx
CRC BYTE
*TO BE TRANSMITTED OR RECEIVED AT OVERDRIVE SPEED IF OD = 1.
** PRESENCE PULSE IS SHORT IF OD = 1.
DS1921G Tx
FAMILY CODE
(1 BYTE)
DS1921G Tx
SERIAL NUMBER
(6 BYTES)
OD = 0
MASTER Tx BIT 0
Y
SHORT
RESET PULSE?
YY
Y
Y
Y
Y
N
33h
READ ROM
COMMAND?
N
55h
MATCH ROM
COMMAND?
BIT 0 MATCH? BIT 0 MATCH?
N
N N
N N
N N
F0h
SEARCH ROM
COMMAND?
N
ECh
CONDITIONAL SEARCH
COMMAND?
N
Y
MASTER Tx BIT 1
MASTER Tx BIT 63
BIT 1 MATCH?
BIT 63 MATCH?
Y
Y
FROM MEMORY/CONTROL
FUNCTIONS FLOWCHART (FIGURE 10)
TO MEMORY FUNCTIONS
FLOWCHART (FIGURE 10)
DS1921G Tx BIT 0
DS1921G Tx BIT 0
MASTER Tx BIT 0
BIT 1 MATCH?
BIT 63 MATCH?
DS1921G Tx BIT 1
DS1921G Tx BIT 1
MASTER Tx BIT 1
DS1921G Tx BIT 63
DS1921G Tx BIT 63
MASTER Tx BIT 63
Y
BIT 0 MATCH?
N
N
N
Y
Y
DS1921G Tx BIT 0
DS1921G Tx BIT 0
MASTER Tx BIT 0
CONDITION
MET?
N
Y
BIT 1 MATCH?
BIT 63 MATCH?
DS1921G Tx BIT 1
DS1921G Tx BIT 1
MASTER Tx BIT 1
DS1921G Tx BIT 63
DS1921G Tx BIT 63
MASTER Tx BIT 63
Y
FROM FIGURE 13b
TO FIGURE 13b
TO FIGURE 13b
FROM FIGURE 13b
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
**
*
*
*
*
*
*
*
Figure 13a. ROM Functions Flowchart