pca24s08a NXP Semiconductors, pca24s08a Datasheet - Page 10

• Manufacturer Part Number: pca24s08a
• Description: 1024 ? 8-bit Cmos Eeprom With Access Protection
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA24S08A_1
Product data sheet
6.4.2.1 Block 0 write protection bits
The PCA24S08A provides a mechanism to divide block 0 into eight 128-bit (16-byte)
pages that can be individually protected against writes. These eight write protection
(WPN) bits are stored within a byte of the access protection page and are organized such
that the LSB protects the first 128 bits, and so on. If a bit in this byte is set to a one and the
PB0 field is set to 11b, then writes are permitted on the page corresponding to the WPN
bit. If the WPN bit is set to a logic 0 or the PB0 is any value other than 11b, then writes are
not permitted in that page.
The Write Protection hierarchy for serial accesses is shown in
the bits within the boxes to the left of the arrows are the only thing that determine whether
or not the bit in the box to the right of the arrow can be written. Read access control is not
shown in this diagram. Addresses listed in this diagram are for the serial port assuming
that the R/W bit in the command byte is set to ‘0’.
Fig 10. Write protection example
SBAP
SBAP
SB0
SB1
SB7
SB0
SB1
SB7
PBAP
PBAP
PB0
PB1
PB7
Rev. 01 — 19 January 2010
WPN0
WPN1
WPN7
WP
1024 × 8-bit CMOS EEPROM with access protection
SB0
SB1
SB7
SBAP
128 bytes
128 bytes
16 bytes
16 bytes
16 bytes
16 bytes
ID page
Block 1
Block 7
7 bytes
Page 0
Page 1
Page 7
Figure
PCA24S08A
PBAP B808
PB0 B800
PB1 B801
PB7 B807
10. In this drawing
© NXP B.V. 2010. All rights reserved.
A800
A80F
A810
A81F
A870
A87F
A880
A8FF
AE80
AEFF
B809
B80F
B810
B81F
Block 0
Access
Protection
Page
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