24AA52_05 Datasheet, PDF (9/28 Pages) Microchip Technology – 2K 2.2V I2C™ Serial EEPROM with Software Write-Protect

24AA52/24LCS52
6.0 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.
6.1 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 6-1, 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 6-1:
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
6.2 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 6-2. 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 1μS 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
© 2005 Microchip Technology Inc.
DS21166J-page 9