DS3902 Maxim Integrated Products, DS3902 Datasheet - Page 10

• Manufacturer Part Number: DS3902
• Description: Dual, NV, Variable Resistors With User EePROM
• Manufacturer: Maxim Integrated Products

See Figure 2 for a read example using the repeated
START condition to specify the starting memory location.
Reading Multiple Bytes from a Slave: The read oper-
ation can be used to read multiple bytes with a single
transfer. When reading bytes from the slave, the master
simply ACKs the data byte if it desires to read another
byte before terminating the transaction. After the master
reads the last byte it NACKs to indicate the end of the
transfer and generates a stop condition. This can be
done with or without modifying the address counter’s
location before the read cycle.
Dual, NV, Variable Resistors
with User EEPROM
Figure 2. I
10
D)
A)
B)
C)
D)
TYPICAL 2-WIRE WRITE TRANSACTION
EXAMPLE 2-WIRE TRANSACTIONS (WHEN ADD_SEL TIED TO GND)
START
TWO BYTE READ
- READ BOTH RESISTORS IN ONE
TRANSACTION.
SINGLE BYTE WRITE
-WRITE RESISTOR 0 TO MID
POSITION (7FH)
SINGLE BYTE READ
-READ RESISTOR 1
SINGLE BYTE WRITE
-SET RESISTOR 1 TO HI-Z
TWO BYTE WRITE
- ENTER THE PASSWORD.
____________________________________________________________________
MSB
1
2
C Communication Examples
0
1
ADDRESS*
SLAVE
0
0
START
START
START 1 0 1 0 0 0 1 0
START
START
0
1 0 1 0 0 0 1 0
1 0 1 0 0 0 1 0
1 0 1 0 0 0 1 0
1 0 1 0 0 0 1 0
1
A2h
A2h
A2h
A2h
A2h
READ/
WRITE
R/W
LSB
SLAVE
ACK
SLAVE
SLAVE
SLAVE
SLAVE
SLAVE
ACK
ACK
ACK
ACK
ACK
MSB
b7
0 0 0 0 0 0 1 0
0 0 0 0 0 0 1 0
0 0 0 0 0 0 1 1
0 0 0 0 0 1 0 0
0 0 0 0 0 0 0 1
b6
02h
03h
01h
04h
02h
b5
REGISTER ADDRESS
* THE ADDRESS IS DETERMINED BY THE ADD_SEL PIN. THE EXAMPLES ASSUME ADD_SEL IS TIED TO
GND. IF THE ADD_SEL PIN WERE INSTEAD CONNECTED TO V
BY THE SLAVE ADDRESS REGISTER.
b4
SLAVE
SLAVE
SLAVE
SLAVE
SLAVE
ACK
ACK
ACK
ACK
ACK
b3
0 0 0 0 0 0 1 0
0 1 1 1 1 1 1 1
REPEATED
REPEATED
b2
PW MSB
START
START
7Fh
02h
By taking advantage of the resistor’s high-impedance
state, the resistors can be used as a digitally controlled
switch. Setting the resistor to position 0 is equivalent to
a logic low level. By using an external pull-up resistor, a
logic high level can be generated by setting the resistor
to the High-Z state.
To achieve best results, it is highly recommended that a
decoupling capacitor is used on the IC power supply
pins. Typical values of decoupling capacitors are 0.01µF
and 0.1µF. Use a high-quality, ceramic, surface-mount
capacitor, and mount it as close as possible to the V
and GND pins of the IC to minimize lead inductance.
b1
LSB
b0
1 0 1 0 0 0 1 1
1 0 1 0 0 0 1 1
SLAVE
SLAVE
SLAVE
ACK
ACK
ACK
A3h
A3h
SLAVE
ACK
STOP
STOP
PW LSB
MSB
b7
SLAVE
SLAVE
Using the Resistors as a Switch
ACK
ACK
b6
Application Information
RES VALUE
SLAVE
b5
CC
ACK
DATA
RES 0
DATA
. THEN THE ADDRESS WOULD BE DETERMINED
Power Supply Decoupling
b4
DATA
STOP
b3
MASTER
MASTER
NACK
ACK
b2
b1
STOP
DATA
RES 1
LSB
b0
SLAVE
ACK
MASTER
NACK
STOP
STOP
CC