DS3231 datasheet(16/19 Pages) DALLAS

16 / 19 page

Figures 3 and 4 detail how data transfer is accom-

plished on the I2C bus. Depending upon the state of

the R/W bit, two types of data transfer are possible:

Data transfer from a master transmitter to a slave

receiver. The first byte transmitted by the master is

the slave address. Next follows a number of data

bytes. The slave returns an acknowledge bit after

each received byte. Data is transferred with the most

significant bit (MSB) first.

Data transfer from a slave transmitter to a master

receiver. The first byte (the slave address) is trans-

mitted by the master. The slave then returns an

acknowledge bit. Next follows a number of data

bytes transmitted by the slave to the master. The

master returns an acknowledge bit after all received

bytes other than the last byte. At the end of the last

received byte, a not acknowledge is returned.

The master device generates all the serial clock puls-

es and the START and STOP conditions. A transfer is

ended with a STOP condition or with a repeated

START condition. Since a repeated START condition

is also the beginning of the next serial transfer, the

bus will not be released. Data is transferred with the

most significant bit (MSB) first.

The DS3231 can operate in the following two modes:

Slave receiver mode (DS3231 write mode): Serial

data and clock are received through SDA and SCL.

After each byte is received, an acknowledge bit is

transmitted. START and STOP conditions are recog-

nized 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 the START condition. The slave

address byte contains the 7-bit DS3231 address,

which is 1101000, followed by the direction bit (R/W),

which is 0 for a write. After receiving and decoding

the slave address byte, the DS3231 outputs an

Extremely Accurate I2C-Integrated

RTC/TCXO/Crystal

____________________________________________________________________

STOP

CONDITION

OR REPEATED

START

CONDITION

REPEATED IF MORE BYTES

ARE TRANSFERED

ACK

START

CONDITION

ACK

ACKNOWLEDGEMENT

SIGNAL FROM RECEIVER

ACKNOWLEDGEMENT

SIGNAL FROM RECEIVER

SLAVE ADDRESS

MSB

SCL

SDA

R/W

DIRECTION

BIT

3–7

Figure 2. I2C Data Transfer Overview

XXXXXXXX

1101000

XXXXXXXX A XXXXXXXX A XXXXXXXX A P

<SLAVE

ADDRESS>

S = START

A = ACKNOWLEDGE

P = STOP

R/W = READ/WRITE OR DIRECTION BIT ADDRESS = D0H

DATA TRANSFERRED

(X + 1 BYTES + ACKNOWLEDGE)

<WORD

ADDRESS (n)>

Figure 3. Slave Receiver Mode (Write Mode)

XXXXXXXX

1101000

XXXXXXXX A XXXXXXXX A XXXXXXXX A P

<SLAVE

ADDRESS>

S = START

A = ACKNOWLEDGE

P = STOP

A = NOT ACKNOWLEDGE

R/W = READ/WRITE OR DIRECTION BIT ADDRESS = D1H

DATA TRANSFERRED

(X + 1 BYTES + ACKNOWLEDGE)

NOTE: LAST DATA BYTE IS FOLLOWED BY

A NOT ACKNOWLEDGE (A) SIGNAL

Figure 4. Slave Transmitter Mode (Read Mode)

DS3231 Datasheet(PDF) 16 Page - Dallas Semiconductor

DS3231 Datasheet(HTML) 16 Page - Dallas Semiconductor

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Datasheet Download

Link URL