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BR24T1MFJ-3AM

Serial EEPROM Series Standard EEPROM I2C BUS EEPROM (2-Wire)

ROHM Semiconductor 

BR24T1M-3AM

Datasheet

Timing Chart

1. I2C BUS Data Communication

I2C BUS data communication starts by start condition input, and ends by stop condition input. Data is always 8bit long,

and acknowledge is always required after each byte. I2C BUS data communication with several devices is possible by

connecting with 2 communication lines: serial data (SDA) and serial clock (SCL).

Among the devices, there should be a “master” that generates clock and control communication start and end. The rest

become “slave” which are controlled by an address peculiar to each device, like this EEPROM. The device that outputs

data to the bus during data communication is called “transmitter”, and the device that receives data is called “receiver”..

SDA

1-7

8

9

1-7

8

9

1-7

8

SCL

S

START ADDRESS

condition

R/W ACK

DATA

ACK

DATA

Figure 35. Data Transfer Timing

9

P

ACK STOP

condition

2. Start Condition (Start Bit Recognition)

(1) Before executing each command, start condition (start bit) where SDA goes from 'HIGH' down to 'LOW' when

SCL is 'HIGH' is necessary.

(2) This IC always detects whether SDA and SCL are in start condition (start bit) or not, therefore, unless this

condition is satisfied, any command cannot be executed.

3. Stop Condition (Stop Bit Recognition)

(1) Each command can be ended by a stop condition (stop bit) where SDA goes from 'LOW' to 'HIGH' while SCL is

'HIGH'.

4. Acknowledge (ACK) Signal

(1) This acknowledge (ACK) signal is a software rule to show whether data transfer has been made normally or not.

In master-slave communication, the device (Ex. µ-COM sends slave address input for write or read command to

this IC) at the transmitter (sending) side releases the bus after output of 8bit data.

(2) The device (Ex. This IC receives the slave address input for write or read command from the µ-COM) at the

receiver (receiving) side sets SDA 'LOW' during 9th clock cycle, and outputs acknowledge signal (ACK signal)

showing that it has received the 8bit data.

(3) This IC, after recognizing start condition and slave address (8bit), outputs acknowledge signal (ACK signal)

'LOW'.

(4) After receiving 8bit data (word address and write data) during each write operation, this IC outputs acknowledge

signal (ACK signal) 'LOW'.

(5) During read operation, this IC outputs 8bit data (read data), and detects acknowledge signal (ACK signal) 'LOW'.

When acknowledge signal (ACK signal) is detected, and stop condition is not sent from the master (µ-COM) side,

this IC continues to output data. When acknowledge signal (ACK signal) is not detected, this IC stops data

transfer, and recognizes stop condition (stop bit), and ends read operation. Then this IC becomes ready for

another transmission.

5. Device Addressing

(1) Slave address comes after start condition from master.

(2) The significant 4 bits of slave address are used for recognizing a device type.

The device code of this IC is fixed to '1010'.

(3) Next slave addresses (A2 A1 --- device address) are for selecting devices, and plural ones can be used on a

same bus according to the number of device addresses.

(4) The most insignificant bit (R/W --- READ/WRITE) of slave address is used for designating write or read action,

and is as shown below.

Setting R /

――

W

to 0 ------- write (setting 0 to word address setting of random read)

Setting R /

――

W

to 1 ------- read

Type

BR24T1M-3AM

Slave address

1 0 1 0 A2 A1 P0 R/―W―

Maximum number of

Connected buses

4

P0 is page select bit.

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TSZ22111・15・001

14/28

TSZ02201-0GFG0G100430-1-2

08.Jul.2016 Rev.001

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