BR24A□□-WM series

Technical Note

11/17

www.rohm.com

2009.08 - Rev.C

© 2009 ROHM Co., Ltd. All rights reserved.

●

Software reset

Software reset is executed when to avoid malfunction after power on, and to reset during command input. Software reset

has several kinds, and 3 kinds of them are shown in the figure below. (Refer to Fig.47(a), Fig.47(b), and Fig.47(c).) In

dummy clock input area, release the SDA bus ('H' by pull up). In dummy clock area, ACK output and read data '0' (both 'L'

level) may be output from EEPROM, therefore, if 'H' is input forcibly, output may conflict and over current may flow, leading

to instantaneous power failure of system power source or influence upon devices.

●

Acknowledge polling

During internal write execution, all input commands are ignored, therefore ACK is not sent back. During internal automatic

write execution after write cycle input, next command (slave address) is sent, and if the first ACK signal sends back 'L', then

it means end of write action, while if it sends back 'H', it means now in writing. By use of acknowledge polling, next

command can be executed without waiting for tWR = 5ms.

When to write continuously, R/W = 0, when to carry out current read cycle after write, slave address R/W = 1 is sent, and if

ACK signal sends back 'L', then execute word address input and data output and so forth.

Fig.48 Case to continuously write by acknowledge polling

1

2

13

14

SCL

Dummy clock×14

Start×2

Fig.47-(a) The case of dummy clock +START+START+ command input

※

Start command from START input.

2

1

8

9

Dummy clock×9

Start

Fig.47-(b) The case of START +9 dummy clocks +START+ command input

Start

Normal command

Normal command

Normal command

Normal command

Start×9

SDA

1

2

3

8

9

7

Fig.47-(c) START×9+ command input

Normal command

Normal command

SCL

SDA

SCL

SDA

S

T

A

R

T

First write command

A

C

K

H

Slave

address

Slave

address

Write command

During internal write,

ACK = HIGH is sent back.

Second write command

S

T

A

R

T

S

T

A

R

T

S

T

O

P

S

T

O

P

A

C

K

H

A

C

K

H

A

C

K

L

A

C

K

L

Slave

address

Word

address

…

A

C

K

L

Slave

address

Data

After completion of internal write,

ACK=LOW is sent back, so input next

word address and data in succession.

S

T

A

R

T

S

T

A

R

T

S

T

O

P

A

C

K

H

A

C

K

L