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PDF X24257 Data sheet ( Hoja de datos )
| Número de pieza | X24257 | |
| Descripción | 400kHz 2-Wire Serial EEPROM | |
| Fabricantes | Xicor | |
| Logotipo |  |
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Preliminary Information
256K
X24257
400kHz 2-Wire Serial EEPROM with Block Lock™
32K x 8 Bit
FEATURES
• Save critical data with programmable block lock
protection
—Block lock (first page, first 2 pages, first 4
pages, first 8 pages, 1/4, 1/2, or all of EEPROM
array)
—Software write protection
—Programmable hardware write protect
• In circuit programmable ROM mode
• 400kHz 2-wire serial interface
—Schmitt trigger input noise suppression
—Output slope control for ground bounce noise
elimination
• Longer battery life with lower power
—Active read current less than 1µA
—Active write current less than 3µA
—Standby current less than 1µA
• 2.5V to 5.5V power supply
• 64-byte page write mode
—Minimizes total write time per word
• Internally organized 32K x 8
• Bidirectional data transfer protocol
• Self-timed write cycle
—Typical write cycle time of 5ms
• High reliability
—Endurance: 100,000 cycles
—Data retention: 100 years
• 8-lead XBGA, 8-lead SOIC, 14-lead TSSOP
DESCRIPTION
The X24257 is a CMOS Serial EEPROM, internally
organized 32K x 8. The device features a serial inter-
face and software protocol allowing operation on a
simple two wire bus.
Three device select inputs (S0–S1) allow up to four
devices to share a common two wire bus.
A Write Protect Register at the highest address location,
FFFFh, provides three write protection features: Software
Write Protect, Block Lock Protect, and Programmable
Hardware Write Protect. The Software Write Protect
feature prevents any nonvolatile writes to the device
until the WEL bit in the Write Protect Register is set.
The Block Lock Protection feature gives the user eight
array block protect options, set by programming three
bits in the Write Protect Register. The Programmable
Hardware Write Protect feature allows the user to
install the device with WP tied to VCC, write to and
Block Lock the desired portions of the memory array in
circuit, and then enable the In Circuit Programmable
ROM Mode by programming the WPEN bit HIGH in the
Write Protect Register. After this, the Block Locked
portions of the array, including the Write Protect Register
itself, are protected from being erased if WP is high.
Xicor EEPROMs are designed and tested for applica-
tions requiring extended endurance. Inherent data
retention is greater than 100 years.
BLOCK DIAGRAM
Serial EEPROM Data
and Address (SDA)
SCL
S1
S0
Command
Decode
and
Control
Logic
Block Lock and
Write Protect
Control Logic
Device
Select
Logic
Page
Decode
Logic
Write
Protect
Register
WP
Data Register
Y Decode Logic
Serial EEPROM
Array
32K X 8
Write Voltage
Control
REV 1.1.1 10/15/00
www.xicor.com
Characteristics subject to change without notice. 1 of 19
1 page  
www.DataSheet4U.com
X24257 – Preliminary Information
WRITE OPERATIONS
Byte Write
For a write operation, the device follows “3 byte” proto-
col, consisting of one Slave Address Byte, one Word
Address Byte 1, and the Word Address Byte 0, which
gives the master access to any one of the words in the
array. Upon receipt of the Word Address Byte 0, the
device responds with an acknowledge, and waits for
the first eight bits of data. After receiving the 8 bits of
the data byte, the device again responds with an
acknowledge. The master then terminates the transfer
by generating a stop condition, at which time the
device begins the internal write cycle to the nonvolatile
memory. While the internal write cycle is in progress
the device inputs are disabled and the device will not
respond to any requests from the master. The SDA pin
is at high impedance. See Figure 5.
Page Write
The device is capable of a 64 byte page write operation.
It is initiated in the same manner as the byte write
operation; but instead of terminating the write operation
after the first data word is transferred, the master can
transmit up to sixty-three more words. The device will
respond with an acknowledge after the receipt of each
word, and then the byte address is internally incre-
mented by one. The page address remains constant.
When the counter reaches the end of the page, it “rolls
over” and goes back to the first byte of the current
page. This means that the master can write 64-bytes to
the page beginning at any byte. If the master begins
writing at byte 32, and loads 64-bytes, then the first
32-bytes are written to bytes 32 through 63, and the
last 16 words are written to bytes 0 through 31. After-
wards, the address counter would point to byte 32. If the
master writes more than 64 bytes, then the previously
loaded data is overwritten by the new data, one byte at
a time.
The master terminates the data byte loading by issuing
a stop condition, which causes the device to begin the
nonvolatile write cycle. As with the byte write operation,
all inputs are disabled until completion of the internal
write cycle. Refer to Figure 6 for the address, acknowl-
edge, and data transfer sequence.
Figure 5. Byte Write Sequence
Signals from
the Master
SDA Bus
Signals from
the Slave
S
T
A
R
Slave
Address
T
Word Address
Byte 1
S 1 0 1 0 0 S1S0 0
A
C
K
Word Address
Byte 0
A
C
K
A
C
K
Data
S
T
O
P
P
A
C
K
Figure 6. Page Write Sequence
Signals from
the Master
SDA Bus
Signals from
the Slave
S
T
A
R
Slave
Address
T
Word Address
Byte 1
Word Address
Byte 0
S 1 0 1 0 0 S1S0 0
AAA
CCC
KKK
Data
(0)
A
C
K
(0 ≤ n ≤ 64)
Data
(n)
S
T
O
P
P
A
C
K
REV 1.1.1 10/15/00
www.xicor.com
Characteristics subject to change without notice. 5 of 19
5 Page 
www.DataSheet4U.com
X24257 – Preliminary Information
ABSOLUTE MAXIMUM RATINGS
Temperature under bias ................... –65°C to +135°C
Storage temperature ........................ –65°C to +150°C
Voltage on any pin with
respect to VSS .........................................–1V to +7V
D.C. output current ............................................... 5mA
Lead temperature
(soldering, 10 seconds).................................. 300°C
COMMENT
Stresses above those listed under “Absolute Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only and the functional operation of
the device at these or any other conditions above those
indicated in the operational sections of this specification
is not implied. Exposure to absolute maximum rating con-
ditions for extended periods may affect device reliability.
RECOMMENDED OPERATING CONDITIONS
Temperature
Commercial
Industrial
Min.
0°C
–40°C
Max.
+70°C
+85°C
Supply Voltage
X24257–2.5
Limits
2.5V to 5.5V
D.C. OPERATING CHARACTERISTICS VCC equals the range indicated for each device type, unless otherwise stated.
Symbol
Parameter
VCC = 2.5 to 5.5V
Min.
Max.
Unit
Test Conditions
ICC1
ICC2
ISB1(2)
Active Supply Current
(Read)
Active Supply Current
(Write)
Standby Current AC
1 mA VIL = VCC X 0.1
VIH = VCC X 0.9
3 mA fSCL = 400kHz
SDA = Open
1 mA VIL = VCC X 0.1
VIH = VCC X 0.9
fSCL = 400kHz
SDA = Open
VSB
ISB2(2)
ILI
ILO
VlL(3)
VIH(3)
VHYS
Standby Voltage (Test)
Standby Current DC
Input Leakage Current
Output Leakage Current
Input LOW Voltage
Input HIGH Voltage
Schmitt Trigger Input
Hysteresis
Fixed input level
VCC– 0.2
–0.5
VCC x 0.7
0.2
1
10
10
VCC x 0.3
VCC + 0.5
V
mA VSDA = VSCL = VSB,
Others = GND or VSB
mA VIN = GND to VCC
mA VSDA = GND to VCC
Device is in Standby(2)
V
V
V
VCC related level
VOL Output LOW Voltage
VCC x 0.05
0.4
V
V IOL = 3mA
REV 1.1.1 10/15/00
www.xicor.com
Characteristics subject to change without notice. 11 of 19
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet X24257.PDF ] | |
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