NM24C08U Datasheet, PDF (9/13 Pages) Fairchild Semiconductor – 8K-Bit Serial EEPROM 2-Wire Bus Interface

Write Cycle Timing (Continued)
The NM24C08U/09U device will always respond with an acknowl-
edge after recognition of a start condition and its slave address. If
both the device and a write operation have been selected, the
NM24C08U/09U will respond with an acknowledge after the
receipt of each subsequent eight bit byte.
In the read mode the NM24C08U/09U slave will transmit eight bits
of data, release the SDA line and monitor the line for an acknowl-
edge. If an acknowledge is detected and no stop condition is
generated by the master, the slave will continue to transmit data.
If an acknowledge is not detected, the slave will terminate further
data transmissions and await the stop condition to return to the
standby power mode.
Device Addressing
Following a start condition the master must output the address of
the slave it is accessing. The most significant four bits of the slave
address are those of the device type identifier (see Figure 5). This
is fixed as 1010 for all EEPROM devices.
Slave Addresses (Figure 5)
Device Type
Identifier
Device
Address
Refer to the following table for Slave Addresses string details:
Device A0 A1 A2 Page Page Block
Blocks Addresses
NM24C08U/09U P P A
4
00 01 10 11
A: Refers to a hardware configured Device Address pin
P: Refers to an internal PAGE BLOCK memory segment.
All IIC EEPROMs use an internal protocol that defines a PAGE
BLOCK size of 2K bits (for Word addressess 0000 through 1111).
Therefore, address bits A0, A1, or A2 (if designated 'P') are used
to access a PAGE BLOCK in conjunction with the Word address
used to access any individual data byte (Word).
The last bit of the slave address defines whether a write or read
condition is requested by the master. A '1' indicates that a read
operation is to be executed, and a '0' initiates the write mode.
A simple review: After the NM24C08U/09U recognizes the start
condition, the devices interfaced to the IIC bus wait for a slave
address to be transmitted over the SDA line. If the transmitted
slave address matches an address of one of the devices, the
designated slave pulls the line LOW with an acknowledge signal
and awaits further transmissions.
1
01
NM24C08U/09U
0 A2 A1 A0 R/W (LSB)
Page
Block Address
DS800009-14
9
NM24C08U/09U Rev. B.1
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