Technical Note

8/18

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2010.12 - Rev.B

© 2010 ROHM Co., Ltd. All rights reserved.

●Command mode

Command

Contents

Ope code

WREN

Write enable command

0000

0110

WRDI

Write disable command

0000

0100

READ

Read command

0000

0011

WRITE

Write command

0000

0010

RDSR

Read status register command

0000

0101

WRSR

Write status register command

0000

0001

●Timing chart

1. Write enable (WREN) / disable (WRDI) command

This IC has write enable status and write disable status. It is set to write enable status by write enable command, and it is

set to write disable status by write disable command. As for these commands, set CSB LOW, and then input the

respective ope codes. The respective commands are accepted at the 7-th clock rise. Even with input over 7 clocks,

command becomes valid.

When to carry out write command, it is necessary to set write enable status by the write enable command. If write

command is input in the write disable status, the command is cancelled. And even in the write enable status, once write

command is executed, it gets in the write disable status. After power on, this IC is in write disable status.

2. Read command (READ)

Product

number

Address

length

BR25S320-W

A11-A0

BR25S640-W

A12-A0

BR25S128-W

A13-A0

BR25S256-W

A14-A0

By read command, data of EEPROM can be read. As for this command, set CSB LOW, then input address after read ope

code. EEPROM starts data output of the designated address. Data output is started from SCK fall of 23-th clock, and

from D7 to D0 sequentially. This IC has increment read function. After output of data for 1 byte (8bits), by continuing input

of SCK, data of the next address can be read. Increment read can read all the addresses of EEPROM. After reading data

of the most significant address, by continuing increment read, data of the most insignificant address is read.

WREN (WRITE ENABLE): Write enable

Fig.33

Write enable command

High-Z

6

03

7

12

45

CSB

SCK

SO

SI

0

00

001

10

Fig.34

Write disable command

WRDI (WRITE DISABLE): Write disable

High-Z

0

000

SI

0100

03

12

4

7

CSB

SCK

5

6

SO

High-Z

11

1

1

0

0

3

7

1

2

D6

SO

CSB

SCK

SI

4

5

A12

6

8

*

A0

A1

D7

23

30

24

D0

0

0

0

0

0

D2

D1

～ ～

～ ～

～ ～

～ ～

～ ～

～ ～

～ ～

～ ～

～ ～

～ ～

9

10

A13

A14

30

31

Fig.35

Read command