24LLC08
8K-Bit Serial EEPROM
HARDWARE-BASED WRITE PROTECTION
You can also write-protect the entire memory area of the 24LLC08. This method of write protection is controlled
by the state of the Write Protect (WP) pin.
When the WP pin is connected to VCC, any attempt to write a value to the memory is ignored.
The 24LLC08 will acknowledge slave and word address, but it will not generate an acknowledge after receiving
the first byte of the data. Thus the write cycle will not be started when the stop condition is generated. By
connecting the WP pin to VSS, the write function is allowed for the entire memory.
These write protection features effectively change the EEPROM to a ROM in order to prevent data from being
overwritten. Whenever the write function is disabled, a slave address and a word address are acknowledged on
the bus, but data bytes are not acknowledged.
CURRENT ADDRESS BYTE READ OPERATION
The internal word address pointer maintains the address of the last word accessed, incremented by one.
Therefore, if the last access (either read or write) was to the address “n”, the next read operation would access
data at address “n+1”.
When the 24LLC08 receives a slave address with the R/W bit set to “1”, it issues an ACK and sends the eights
bits of data. The master does not acknowledge the transfer but it does generate a Stop condition. In the way,
the 24LLC08 effectively stops the transmission (see Figure 3-12).
Start Slave Address
Data
Stop
A
C
K
N
O
A
C
K
Figure 3-12. Current Address Byte Read Operation
* All specs and applications shown above subject to change without prior notice.
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Rev 1.0 Nov. 18, 2002
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