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AT24C01A/02/04/08/16
0180R–SEEPR–4/04
Device Addressing The 1K, 2 K, 4K, 8K a nd 1 6K EE PRO M dev ic es al l r eq ui re an 8-bit d ev ic e a ddres s wor d
following a start condition to enable the chip for a read or write operation (refer to Figure
1).
The device address word consists of a mandatory one, zero sequence for the first four
most significant bits as shown. This is common to all the EEPROM devices.
The next 3 bits are the A2, A1 and A0 device address bits for the 1K/2K EEPROM.
These 3 bits must compare to their corresponding hard-wired input pins.
The 4K EEPRO M on ly use s the A2 and A1 devi ce ad dres s bi ts with the thir d bi t bein g a
memory page address bit. The two device address bits must compare to their corre-
sponding hard-wired input pins. The A0 pin is no connect.
The 8K EEP ROM only us es the A2 device add ress bit with the next 2 bits bei ng for
memory page addressing. The A2 bit must compare to its corresponding hard-wired
input pin. The A1 and A0 pins are no connect.
The 16K does not use any devi ce addr ess bits but inst ead the 3 bits are us ed for mem-
ory page addressing. These page addressing bits on the 4K, 8K and 16K devices
should be considered the most significant bits of the data word address which follows.
The A0, A1 and A2 pins are no connect.
The eig hth bi t of the dev i ce add r ess is the r ead /write ope ra tio n s elec t bi t. A r ea d o pera-
tion is initiated if this bit is high and a write operation is initiated if this bit is low.
Upon a com pare of the dev ic e ad dres s, th e EE PRO M will ou tpu t a zero . If a compar e is
not made, the chip will return to a standby state.
Write Operations BYTE WRITE: A write operation requires an 8-bit data word address following the
device add ress word and ackn owledg ment. Upo n recei pt of thi s add ress, th e EEPR OM
will again respond with a zero and then clock in the first 8-bit dat a word. Follow ing
receipt of the 8-bit data word, the EEPROM will output a zero and the addressing
device , such a s a micr ocontrol ler, m ust termi nate the wr ite seque nce wi th a stop cond i-
tion. At this time the EEPROM enters an internally timed write cycle, tWR, to the
nonvolatile memory. All inputs are disabled during this write cycle and the EEPROM will
not respond until the write is complete (refer to Figure 2).
PAGE WRITE: The 1K/2K EE PR OM is c apa bl e of an 8- byte page write, and the 4K , 8K
and 16K devices are capable of 16-byte page writes.
A page wri te is in itiate d the same as a byte wr ite, but th e micr ocontro ller does not sen d
a stop condition after the first data word is clocked in. Instead, after the EEPROM
acknowledges receipt of the first data word, the microcontroller can transmit up to seven
(1K/2K) or fifteen (4K, 8K, 16K) more data words. The EEPROM will respond with a zero
after each data word received. The microcontroller must terminate the page write
sequence with a stop condition (refer to Figure 3).
The data word address lower three (1K /2K) or four (4K, 8K, 16K) bits are i nternally
increm ent ed fol lowing the rec ei pt of eac h data wo rd. T h e h igh er d ata word add re ss b its
are not incr emented, retai ning the memor y page row locat ion. When the word address,
internally generated, reaches the page boundary, the following byte is placed at the
beginning of th e same page. If more than eigh t (1K/2K) or sixteen (4K, 8K, 16K ) data
words a re tran smitte d to th e EE PROM, the d ata wor d addr ess wi ll “r oll o ver” a nd prev i-
ous data will be overwritten.