Table 8-2. Device Address Byte Requirements for Accessing the Write Protection Register

Memory Region

Device Type Identifier

Hardware Address

Bits

Don’t

Care

R/W

Select

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 1

Bit 0

Write Protection

Register

1

0

1

1

A2

A1

X

R/W

Note: 

1.

The A1 Address Bit is a “Don’t Care” on the AT24CSW08X when accessing the WPR.

When accessing the Write Protection register, it is required that the A7 and A6 bits of the word address be set to 11b

respectively. The remaining bits of the word address byte are “don’t care” bits as shown in Table 8-3.

Table 8-3. Word Address Byte Requirements for Accessing the Write Protection Register

A7

A6

A5

A4

A3

A2

A1

A0

Write Protection Register

1

1

X

X

X

X

X

X

Following the word address byte are the contents of the 8‑bit Write Protection register. The register format is shown

in Table 8-4 and the WPR bit functions are included in Table 8-5.

Table 8-4. Write Protection Register Format

D7

D6

D5

D4

D3

D2

D1

D0

Read WPR

0

0

0

0

WPRE

WPB1

WPB0

WPRL

Write WPR

0

1

0: No Lock

0

1: Set Lock

Table 8-5. Write-Protect Register Bit Function

Bit

Name

Type

Description

3

WPRE

Write Protection Register

Enable

R/W

0

No Software Write Protection is enabled

(Factory Default).

1

Write protection is set by the state of the

WPB[1:0] bits.

2:1

WPB1

Write-Protect Block Bits

R/W

00

Upper ¼ of EEPROM is write protected

(Factory Default).

01

Upper ½ of EEPROM is write protected.

WPB0

10

Upper ¾ of EEPROM is write protected.

11

Entire EEPROM is write protected.

0

WPRL

Write-Protect Lock Bit

R/OTP

0

WPR can be written to; requires D5 = 0

during write (Factory Default).

1

WPR will become permanently locked

(requires D5 = 1) during write.

• Write-Protect Register Enable bit (WPRE), Bit 3

This bit is used to enable or disable the device software write-protect feature. A logic ‘0’ in this position will

disable software write protection and a logic ‘1’ will enable this function.

• Write-Protect Block Bits (WPB[1:0], Bits 2:1)

AT24CSW04X/AT24CSW08X

Write Protection

and its subsidiaries

Datasheet

DS20006426B-page 23