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