Rainbow Electronics DS3231 - Manual (Page 17)

acknowledge on SDA. After the DS3231 acknowl-
edges the slave address + write bit, the master
transmits a word address to the DS3231. This sets
the register pointer on the DS3231, with the DS3231
acknowledging the transfer. The master may then
transmit zero or more bytes of data, with the DS3231
acknowledging each byte received. The register
pointer increments after each data byte is trans-
ferred. The master generates a STOP condition to
terminate the data write.
Slave transmitter mode (DS3231 read mode): The
first byte is received and handled as in the slave
receiver mode. However, in this mode, the direction
bit indicates that the transfer direction is reversed.
Serial data is transmitted on SDA by the DS3231
while the serial clock is input on SCL. START and
STOP conditions are recognized as the beginning
and end of a serial transfer. Address recognition is
performed by hardware after reception of the slave
address and direction bit. The slave address byte is
the first byte received after the master generates a
START condition. The slave address byte contains
the 7-bit DS3231 address, which is 1101000, fol-
lowed by the direction bit (R/W), which is 1 for a
read. After receiving and decoding the slave
address byte, the DS3231 outputs an acknowledge
on SDA. The DS3231 then begins to transmit data
starting with the register address pointed to by the
register pointer. If the register pointer is not written to
before the initiation of a read mode, the first address
that is read is the last one stored in the register point-
er. The DS3231 must receive a not acknowledge to
end a read.
Handling, PC Board Layout,
and Assembly
The DS3231 package contains a quartz tuning-fork
crystal. Pick-and-place equipment can be used, but
precautions should be taken to ensure that excessive
shocks are avoided. Ultrasonic cleaning should be
avoided to prevent damage to the crystal.
Avoid running signal traces under the package, unless
a ground plane is placed between the package and the
signal line. All N.C. (no connect) pins must be connect-
ed to ground.
Moisture-sensitive packages are shipped from the facto-
ry dry packed. Handling instructions listed on the pack-
age label must be followed to prevent damage during
reflow. See IPC/JEDEC J-STD-020 standard for moisture-
sensitive device (MSD) classifications and reflow pro-
files. Exposure to reflow is limited to 2 times maximum.
DS3231
Extremely Accurate I
2
C-Integrated
RTC/TCXO/Crystal
____________________________________________________________________ 17