DS3901
Triple, 8-Bit NV Variable Resistor
with Dual Settings and User EEPROM
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Reading a Single Byte from a Slave: Unlike the write
operation that uses the memory address byte to define
where the data is to be written, the read operation
occurs at the present value of the memory address
counter. To read a single byte from the slave, the mas-
ter generates a START condition, writes the slave
address byte with R/W = 1, reads the data byte with a
NACK to indicate the end of the transfer, and generates
a STOP condition.
Manipulating the Address Counter for Reads: A
dummy write cycle can be used to force the address
counter to a particular value. To do this, the master
generates a START condition, writes the slave address
byte (R/W = 0), writes the memory address where it
desires to read, generates a repeated START condition,
writes the slave address byte (R/W = 1), reads data
with ACK or NACK as applicable, and generates a
STOP condition.
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.
Applications Information
Power-Supply Decoupling
To achieve best results, it is recommended that the power
supply is decoupled with a 0.01µF or a 0.1µF capacitor.
Use high-quality, ceramic, surface-mount capacitors, and
mount the capacitors as close as possible to the V
CC
and
GND pins to minimize lead inductance.
SDA and SCL Pullup Resistors
SDA is an open-collector output on the DS3901 that
requires a pullup resistor to realize high logic levels. A
master using either an open-collector output with a
pullup resistor or a push-pull output driver can be uti-
lized for SCL. Pullup resistor values should be chosen
to ensure that the rise and fall times listed in the AC
Electrical Characteristics are within specification.
Chip Topology
TRANSISTOR COUNT: 52,353
SUBSTRATE CONNECTED TO GROUND
