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24AA52

2K 2.2V I2C™ Serial EEPROM with Software Write-Protect

Microchip Technology 

24AA52/24LCS52

7.0 WRITE PROTECTION

The 24XXX52 has a software write-protect feature that

allows the lower half of the array (addresses 00h-7Fh)

to be permanently write-protected, as well as a WP pin

that can be used to protect the entire array.

7.1 Software Write-Protect

The software write-protect feature is invoked by writing

to the write-protect register. This is done by sending a

command similar to a normal Write command. As shown

in Figure 7-1, the write-protect register is written by

sending a Write command with the slave address set to

‘0110’ instead of ‘1010’ and the address bits and data

bits are “don’t cares.” Once the software write-protect

register has been written, the device will not

acknowledge the ‘0110’ control byte.

FIGURE 7-1:

SETTING WRITE-PROTECT REGISTER

S

Bus Activity

Master

T

A

R

T

Control

Byte

Word

Address

SDA Line

S01 1 0

Bus Activity

A

A

C

C

K

K

7.2 Resetting the Software

Write-Protect Fuse

It is possible to reset the software write-protect feature

on the 24XXX52. This is done by sending a command

similar to setting the software write-protect command,

except the command is sent before the regular control

byte and is ‘1001’. The full command will be shown in

Figure 7-2. In order for the command to work, a voltage

of Vcc + 5.5V must be applied to the WP pin and must

be sustained for 1S before the command is given. The

customer should also allow for a 5 ms delay after the

Stop bit for TWC.

Data

S

T

O

P

P

A

C

K

DS21166K-page 10

 1996-2011 Microchip Technology Inc.

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