CAT24CXX1/XX2
Advanced
Reset Threshold Voltage
Hardware Data Protection
From the factory the 24CXXX is offered in five different
variations of reset threshold voltages. They are 4.50-
4.75V, 4.25-4.50V, 3.00-3.15V, 2.85-3.00V and 2.55-
2.70V. To provide added flexibility to design engineers
using this product, the 24CXXX is designed with an
additional feature of programming the reset threshold
voltage. This allows the user to change the existing
reset threshold voltage to one of the other four reset
threshold voltages. Once the reset threshold voltage is
selected it will not change even after cycling the power,
unless the user uses the programmer to change the
reset threshold voltage. However, the programming
functionisavailableonlythroughthirdpartyprogrammer
manufacturers. PleasecallCatalystforalistofprogram-
mer manufacturers who support this function.
The 24CXXX is designed with the following hardware
data protection features to provide a high degree of data
integrity.
(1) The24CXXXfeaturesaWPpin.WhenWPpin istied
high the entire memory array becomes write protected
(read only).
(2) The VCC sense provides write protection when VCC
fallsbelowtheresetthresholdvalue(VTH). TheVCC lock
out inhibits writes to the serial EEPROM whenever VCC
falls below (power down) VTH or until VCC reaches the
reset threshold (power up) VTH
.
Figure 2. Bus Timing
t
t
t
F
HIGH
R
t
t
LOW
LOW
SCL
t
t
HD:DAT
SU:STA
t
t
t
t
HD:STA
SU:DAT
SU:STO
SDA IN
BUF
t
t
DH
AA
SDA OUT
Figure 3. Write Cycle Timing
SCL
SDA
8TH BIT
BYTE n
ACK
t
WR
STOP
CONDITION
START
CONDITION
ADDRESS
Figure 4. Start/Stop Timing
SDA
SCL
START BIT
STOP BIT
Doc. No. 25079-00 1/98 M-1
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