AT34C02D_14 Datasheet, PDF (9/25 Pages) ATMEL Corporation – Permanent and Reversible Software Write Protection

7. Device Addressing
The 2K EEPROM device requires an 8-bit device address word following a start condition to enable the chip for
a read or write operation.
The device address word consists of a mandatory ‘1010’ (Ah) sequence for the first four most-significant bits
for normal read and write operations and ‘0110’ (6h) for writing to the software write protect register.
The next three bits are the A₂, A₁, and A₀ device address bits. These three bits must match their corresponding
hard-wired input pins in order for the part to acknowledge.
The eighth bit of the device address is the read/write operation select bit. A read operation is initiated if this bit is
high and a write operation is initiated if this bit is low.
Upon a successful compare of the device address, the EEPROM will acknowledge by outputting a zero. If a
match is not made, the chip will return to a standby state. The device will not acknowledge if the write protect
register has been programmed and the control code is ‘0110’ (6h).
Figure 7-1. Device Address
1 0 1 0 A2 A1 A0 R/W
MSB
LSB
8. 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 acknowledge or 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.
The device will acknowledge a write command, but not write the data, if the software or hardware write
protection has been enabled. The write cycle time must be observed even when the write protection is enabled.
Figure 8-1. Byte Write
S
W
T
R
A
I
R ^Device
T
T Address
E
Word Address
S
T
O
Data
P
SDA LINE
M
L R AM
LA
A
S
S / CS
SC
C
B
BW K B
BK
K
AT34C02D [DATASHEET]
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Atmel-8781C-SEEPROM-AT34C02D-Datasheet_072014