DS3994Z+W Maxim Integrated Products, DS3994Z+W Datasheet - Page 24

• Manufacturer Part Number: DS3994Z+W
• Description: Display Drivers 4-Ch Cold-Cathode Fl uorescent Controller
• Manufacturer: Maxim Integrated Products

Specifications of DS3994Z+W

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Byte Write: A byte write consists of 8 bits of informa-
tion transferred from the master to the slave (most sig-
nificant bit first) plus a 1-bit acknowledgement from the
slave to the master. The 8 bits transmitted by the mas-
ter are done according to the bit-write definition and the
acknowledgement is read using the bit-read definition.
Byte Read: A byte read is an 8-bit information transfer
from the slave to the master plus a 1-bit ACK or NACK
from the master to the slave. The 8 bits of information
that are transferred (most significant bit first) from the
slave to the master are read by the master using the bit
read definition, and the master transmits an ACK using
the bit write definition to receive additional data bytes.
The master must NACK the last byte read to terminate
communication so the slave will return control of SDA to
the master.
Slave Address Byte: Each slave on the I
responds to a slave addressing byte sent immediately
following a start condition. The slave address byte
(Figure 11) contains the slave address in the most signifi-
cant seven bits and the R/W bit in the least significant bit.
The DS3994’s slave address is 101000A
where A
address pin allows the device to respond to one of two
possible slave addresses. By writing the correct slave
address with R/W = 0, the master writes data to the
slave. If R/W = 1, the master reads data from the slave.
If an incorrect slave address is written, the DS3994 will
assume the master is communicating with another I
device and ignore the communications until the next
start condition is sent.
Memory Address: During an I
master must transmit a memory address to identify the
memory location where the slave is to store the data.
The memory address is always the second byte trans-
mitted during a write operation following the slave
address byte.
4-Channel Cold-Cathode
Fluorescent Lamp Controller
24
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0
is the value of the address pin (A
2
C write operation, the
0
(binary),
2
0
C bus
). The
2
C
Writing a Data Byte to a Slave: The master must gen-
erate a start condition, write the slave address byte
(R/W = 0), write the memory address, write the byte of
data, and generate a stop condition. Remember the
master must read the slave’s acknowledgement during
all byte write operations. See Figure 12 for more detail.
Acknowledge Polling: Any time EEPROM is written,
the DS3994 requires the EEPROM write time (t
the stop condition to write the contents to EEPROM.
During the EEPROM write time, the DS3994 will not
acknowledge its slave address because it is busy. It is
possible to take advantage of that phenomenon by
repeatedly addressing the DS3994, which allows the
next byte of data to be written as soon as the DS3994 is
ready to receive the data. The alternative to acknowl-
edge polling is to wait for a maximum period of t
elapse before attempting to write again to the DS3994.
EEPROM Write Cycles: The number of times the
DS3994’s EEPROM can be written before it fails is
specified in the Nonvolatile Memory Characteristics
table. This specification is shown at the worst-case
write temperature. The DS3994 is typically capable of
handling many additional write cycles when the writes
are performed at room temperature.
Reading a Data Byte from a Slave: To read a single
byte from the slave the master generates a start condi-
tion, writes the slave address byte with R/W = 0, writes
the memory address, generates a repeated start condi-
tion, writes the slave address with R/W = 1, reads the
data byte with a NACK to indicate the end of the trans-
fer, and generates a stop condition. See Figure 12 for
more detail.
Figure 11. DS3994’s Slave Address Byte
SIGNIFICANT BIT
MOST
1
7-BIT SLAVE ADDRESS
0
1
0
A
0
0 0 A
PIN VALUE
I
2
0
C Communication
R/W
READ OR WRITE
DETERMINES
W
) after
W
to