DS1921G Maxim, DS1921G Datasheet - Page 29

• Manufacturer Part Number: DS1921G
• Description: The DS1921G Thermochron® iButton® is a rugged, self-sufficient system that measures temperature and records the result in a protected memory section
• Manufacturer: Maxim

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