Two-wire Serial EEPROM
6.
Device Addressing
The 4K and 8K EEPROM device requires an 8-bit device address word following a start condition to enable the chip for
a read or write operation (refer to
).
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 4K EEPROM only uses the A2 and A1 device address bits with the third bit being a memory page address bit. The
two device address bits must compare to their corresponding hard-wired input pins. The A0 pin is no connect.
The 8K EEPROM only uses the A2 device address bit with the next 2 bits being for memory page addressing. The A2
must compare to its corresponding hard-wired input pin. The A1 and A0 pins are no connect.
For the SOT23 Package Offering:
The 4K EEPROM software A2 and A1 bits in the device address word must be set to zero to properly communicate.
The 8K EEPROM software A2 bit in the device address word must be set to zero to properly communicate.
7.
Write Operations
BYTE WRITE:
A write operation requires an 8-bit data word address following the device address word and
acknowledgment. Upon receipt of this address, the EEPROM will again respond with a zero and then clock in the first
8-bit data word. Following receipt of the 8-bit data word, the EEPROM will output a zero and the addressing device,
such as a microcontroller, must terminate the write sequence with a stop condition. At this time the EEPROM enters an
internally timed write cycle, t
WR
, to the nonvolatile memory. All inputs are disabled during this write cycle and the
EEPROM will not respond until the write is complete (see
).
PAGE WRITE:
The 4K/8K EEPROM is capable of an 16-byte page write.
A page write is initiated the same as a byte write, but the microcontroller does not send 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 fifteen 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.
(see
).
The data word address lower four bits are internally incremented following the receipt of each data word. The higher
data word address bits are not incremented, retaining the memory page row location. When the word address,
internally generated, reaches the page boundary, the following byte is placed at the beginning of the same page. If
more than sixteen data words are transmitted to the EEPROM, the data word address will “roll over” and previous data
will be overwritten.
ACKNOWLEDGE POLLING:
Once the internally timed write cycle has started and the EEPROM inputs are disabled,
acknowledge polling can be initiated. This involves sending a start condition followed by the device address word. The
read/write bit is representative of the operation desired. Only if the internal write cycle has completed will the EEPROM
respond with a zero allowing the read or write sequence to continue.
9
5226G–SEEPR–11/09
ATMEL [ ATMEL CORPORATION ]
