Fremont Micro Devices
24C256A
Two-Wire Serial EEPROM
256K (8-bit wide)
FEATURES
Low voltage and low power operations:
FT24C256A:
VCC = 1.8V to 5.5V
64 bytes page write mode.
Partial page write operation allowed.
Internally organized: 32,768 ×8 (256K).
Standard 2-wire bi-directional serial interface.
Schmitt trigger, filtered inputs for noise protection.
Self-timed write cycle (5ms maximum).
1 MHz (2.5V-5V), 400 kHz (1.8V) Compatibility.
Automatic erase before write operation.
Write protect pin for hardware data protection.
High reliability: typically 1,000,000 cycles endurance.
100 years data retention.
Industrial temperature range (-40℃ to 85℃).
Standard 8-lead DIP/SOP/MSOP/TSSOP/UDFN Pb-free packages.
DESCRIPTION
The FT24C256A series are 262,144 bits of serial Electrical Erasable and Programmable Read Only
Memory, commonly known as EEPROM. They are organized as 32,768 words of 8 bits (one byte) each.
The devices are fabricated with proprietary advanced CMOS process for low power and low voltage
applications. These devices are available in standard 8-lead DIP, 8-lead SOP, 8-lead MSOP,8-lead TSSOP
and 8-lead UDFN packages. A standard 2-wire serial interface is used to address all read and write
functions. Our extended VCC range (1.8V to 5.5V) devices enables wide spectrum of applications.
PIN CONFIGURATION
Pin Name
A2, A1, A0
SDA
SCL
WP
NC
Pin Function
Device Address Inputs
Serial Data Input / Open Drain Output
Serial Clock Input
Write Protect
No-Connect
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page1
Fremont Micro Devices
24C256A
All these packaging types come in Pb-free certified.
FT24C256A
A0
A1
A2
GND
1
8
2
7
3
6
4
5
8L
8L
8L
8L
8L
VCC
WP
SCL
SDA
DIP
SOP
MSOP
TSSOP
UDFN
ABSOLUTE MAXIMUM RATINGS
Industrial operating temperature:
-40℃ to 85℃
Storage temperature:
-50℃ to 125℃
Input voltage on any pin relative to ground:
Maximum voltage:
ESD Protection on all pins:
-0.3V to VCC + 0.3V
8V
>2000V
* Stresses exceed those listed under “Absolute Maximum Rating” may cause permanent damage to the
device. Functional operation of the device at conditions beyond those listed in the specification is not
guaranteed. Prolonged exposure to extreme conditions may affect device reliability or functionality.
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page2
Fremont Micro Devices
24C256A
PIN DESCRIPTIONS
(A) SERIAL CLOCK (SCL)
The rising edge of this SCL input is to latch data into the EEPROM device while the falling edge of this
clock is to clock data out of the EEPROM device.
(B) DEVICE / CHIP SELECT ADDRESSES (A2, A1, A0)
These are the chip select input signals for the serial EEPROM devices. Typically, these signals are
hardwired to either VIH or VIL. If left unconnected, they are internally recognized as VIL.
(C) SERIAL DATA LINE (SDA)
SDA data line is a bi-directional signal for the serial devices. It is an open drain output signal and can be
wired-OR with other open-drain output devices.
(D) WRITE PROTECT (WP)
The FT24C256A devices have a WP pin to protect the whole EEPROM array from programming.
Programming operations are allowed if WP pin is left un-connected or input to VIL. Conversely all
programming functions are disabled if WP pin is connected to VIH or VCC. Read operations is not affected
by the WP pin’s input level.
MEMORY ORGANIZATION
The FT24C256A devices have 512 pages. Since each page has 64 bytes, random word addressing to
FT24C256A will require 15 bits data word addresses.
DEVICE OPERATION
(A) SERIAL CLOCK AND DATA TRANSITIONS
The SDA pin is typically pulled to high by an external resistor. Data is allowed to change only when
Serial clock SCL is at VIL. Any SDA signal transition may interpret as either a START or STOP condition
as described below.
(B) START CONDITION
With SCL VIH, a SDA transition from high to low is interpreted as a START condition. All valid
commands must begin with a START condition.
(C) STOP CONDITION
With SCL VIH, a SDA transition from low to high is interpreted as a STOP condition. All valid read or
write commands end with a STOP condition. The device goes into the STANDBY mode if it is after a
read command. A STOP condition after page or byte write command will trigger the chip into the
STANDBY mode after the self-timed internal programming finish (see Figure 1).
(D) ACKNOWLEDGE
The 2-wire protocol transmits address and data to and from the EEPROM in 8 bit words. The EEPROM
acknowledges the data or address by outputting a "0" after receiving each word. The ACKNOWLEDGE
signal occurs on the 9th serial clock after each word.
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page3
Fremont Micro Devices
24C256A
(E) STANDBY MODE
The EEPROM goes into low power STANDBY mode after a fresh power up, after receiving a STOP bit
in read mode, or after completing a self-time internal programming operation.
Figure 1: Timing diagram for START and STOP conditions
SCL
SDA
START
Condition
Data
Valid
Data
Transition
STOP
Condition
Figure 2: Timing diagram for output ACKNOWLEDGE
START Condition
SCL
Data in
Data out
ACK
DEVICE ADDRESSING
The 2-wire serial bus protocol mandates an 8 bits device address word after a START bit condition to invoke
a valid read or write command. The first four most significant bits of the device address must be 1010,
which is common to all serial EEPROM devices. The next three bits are device address bits. These three
device address bits (5th, 6th and 7th) are to match with the external chip select/address pin states. If a match
is made, the EEPROM device outputs an ACKNOWLEDGE signal after the 8th read/write bit, otherwise the
chip will go into STANDBY mode. However, matching may not be needed for some or all device address
bits (5th, 6th and 7th) as noted below. The last or 8th bit is a read/write command bit. If the 8th bit is at VIH
then the chip goes into read mode. If a “0” is detected, the device enters programming mode.
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page4
Fremont Micro Devices
24C256A
WRITE OPERATIONS
(A) BYTE WRITE
A write operation requires two 8-bit data word address following the device address word and
ACKNOWLEDGE signal. Upon receipt of this address, the EEPROM will respond with a “0” and then
clock in the first 8-bit data word. Following receipt of the 8-bit data word, the EEPROM will again output
a “0”. The addressing device, such as a microcontroller, must terminate the write sequence with a
STOP condition. At this time the EEPROM enters into an internally-timed write cycle state. All inputs
are disabled during this write cycle and the EEPROM will not respond until the writing is completed
(figure 3).
(B) PAGE WRITE
The 256K EEPROM are capable of 64-byte page write.
A page write is initiated the same way as a byte write, but the microcontroller does not send a STOP
condition after the first data word is clocked in. The microcontroller can transmit up to 63 more data
words after the EEPROM acknowledges receipt of the first data word. The EEPROM will respond with a
“0” after each data word is received. The microcontroller must terminate the page write sequence with a
STOP condition (see Figure 4).
The lower six bits of the data word address 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.
If more than 64 data words are transmitted to the EEPROM, the data word address will “roll over” and
the previous data will be overwritten.
(C) ACKNOWLEDGE POLLING
ACKNOWLEDGE polling may be used to poll the programming status during a self-timed internal
programming. By issuing a valid read or write address command, the EEPROM will not acknowledge at
the 9th clock cycle if the device is still in the self-timed programming mode. However, if the programming
completes and the chip has returned to the STANDBY mode, the device will return a valid
ACKNOWLEDGE signal at the 9th clock cycle.
READ OPERATIONS
The read command is similar to the write command except the 8th read/write bit in address word is set to “1”.
The three read operation modes are described as follows:
(A) CURRENT ADDRESS READ
The EEPROM internal address word counter maintains the last read or write address plus one if the
power supply to the device has not been cut off. To initiate a current address read operation, the microcontroller issues a START bit and a valid device address word with the read/write bit (8th) set to “1”. The
EEPROM will response with an ACKNOWLEDGE signal on the 9th serial clock cycle. An 8-bit data word
will then be serially clocked out. The internal address word counter will then automatically increase by
one. For current address read the micro-controller will not issue an ACKNOWLEDGE signal on the 18th
clock cycle. The micro-controller issues a valid STOP bit after the 18th clock cycle to terminate the read
operation. The device then returns to STANDBY mode (see Figure 5).
(B) SEQUENTIAL READ
The sequential read is very similar to current address read. The micro-controller issues a START bit
and a valid device address word with read/write bit (8th) set to “1”. The EEPROM will response with an
ACKNOWLEDGE signal on the 9th serial clock cycle. An 8-bit data word will then be serially clocked out.
Meanwhile the internally address word counter will then automatically increase by one.
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page5
Fremont Micro Devices
24C256A
Unlike current address read, the micro-controller sends an ACKNOWLEDGE signal on the 18th clock
cycle signaling the EEPROM device that it wants another byte of data. Upon receiving the
ACKNOWLEDGE signal, the EEPROM will serially clocked out an 8-bit data word based on the
incremented internal address counter. If the micro-controller needs another data, it sends out an
ACKNOWLEDGE signal on the 27th clock cycle. Another 8-bit data word will then be serially clocked
out. This sequential read continues as long as the micro-controller sends an ACKNOWLEDGE signal
after receiving a new data word. When the internal address counter reaches its maximum valid address,
it rolls over to the beginning of the memory array address. Similar to current address read, the microcontroller can terminate the sequential read by not acknowledging the last data word received, but
sending a STOP bit afterwards instead (figure 6).
(C) RANDOM READ
Random read is a two-steps process. The first step is to initialize the internal address counter with a
target read address using a “dummy write” instruction. The second step is a current address read.
To initialize the internal address counter with a target read address, the micro-controller issues a START
bit first, follows by a valid device address with the read/write bit (8th) set to “0”. The EEPROM will then
acknowledge. The micro-controller will then send two address words. Again the EEPROM will
acknowledge. Instead of sending a valid written data to the EEPROM, the micro-controller performs a
current address read instruction to read the data. Note that once a START bit is issued, the EEPROM
will reset the internal programming process and continue to execute the new instruction - which is to
read the current address (figure 7).
Figure 3: Byte Write
S
T
A
R
T
DEVICE
ADDRESS
W
R
I
T
E
SDA LINE
FIRST WORD
ADDRESS
SECOND WORD
ADDRESS
S
T
O
P
DATA
*
LRA
S / C
B WK
M
S
B
M
S
B
A
C
K
LA
SC
BK
A
C
K
Figure 4: Page Write
S
T
A
R
T
DEVICE
ADDRESS
W
R
I
T
E
FIRST WORD
ADDRESS(N)
SECOND WORD
ADDRESS(N)
S
T
O
DATA(N+X) P
DATA(N)
...
*
SDA LINE
M
S
B
LRA
S / C
B WK
© 2016 Fremont Micro Devices Inc.
M
S
B
A
C
K
LA
SC
BK
A
C
K
A
C
K
DS24C256-A2-page6
Fremont Micro Devices
24C256A
Figure 5: Current Address Read
S
T
A
R
T
DEVICE
ADDRESS
R
E
A
D
S
T
O
P
DATA
SDA LINE
N
O
L RA
S / C
B WK
M
S
B
A
C
K
Figure 6: Sequential Read
DEVICE
ADDRESS
R
E
A
D
DATA (N)
DATA (N+1)
DATA (N+2)
S
T
O
P
DATA (N+3)
SDA LINE
RA
/ C
WK
A
C
K
A
C
K
N
O
A
C
K
A
C
K
Figure 7: Random Read
S
T
A
R
T
DEVICE
ADDRESS
W
R
I
T
E
FIRST WORD
ADDRESS(N)
SECOND WORD
ADDRESS(N)
S
T
A
R
T
DEVICE
ADDRESS
R
E
A
D
S
T
O
P
DATA (N)
*
SDA LINE
M
S
B
LRA
S / C
B WK
M
S
B
A
C
K
L A
S C
B K
M
S
B
LRA
S / C
B WK
N
O
A
C
K
Notes: 1) * = Don’t Care bits
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page7
Fremont Micro Devices
24C256A
Figure 8: SCL and SDA Bus Timing
tF
t HIGH
tLOW
SCL
t SU,STA
t HD.STA
tR
tLOW
t HD.DAT
t SU.DAT
t SU.STO
SDA IN
t AA
t DH
t BUF
SDA OUT
Electrical Specifications
(A)Power-Up Requirements
During a power-up sequence, the VCC supplied to the device should monotonically rise from GND to
the minimum VCC level, with a slew rate no faster than 0.05 V/μs and no slower then 0.1 V/ms. A
decoupling cap should be connected to the VCC PAD which is no smaller than 10nF.
(B)Device Reset
To prevent inadvertent write operations or any other spurious events from occurring during a powerup sequence, this device includes a Power-on Reset (POR) circuit. Upon power-up, the device will
not respond to any commands until the VCC level crosses the internal voltage threshold (VPOR) that
brings the device out of Reset and into Standby mode. The system designer must ensure the
instructions are not sent to the device until the VCC supply has reached a stable value greater than or
equal to the minimum VCC level.
t POFF
VCC
0
t PWR,R
t PUP
0
0
SCL
SDA
Figure 11: Power on and Power down
If an event occurs in the system where the VCC level supplied to the device drops below the
maximum VPOR level specified, it is recommended that a full power cycle sequence be performed by
first driving the VCC pin to GND, waiting at least the minimum tPOFF time and then performing a new
power-up sequence in compliance with the requirements defined in this section.
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page8
Fremont Micro Devices
24C256A
AC CHARACTERISTICS
Symbol
1.8V
Parameter
Min
fSCL
tLOW
Clock frequency, SCL
tHIGH
tI
tAA
tBUF
tHD.STA
tSU.STA
tHD.DAT
tSU.DAT
tR
tF
tSU.STO
tDH
tPWR,R
Endurance
)
1000
kHz
µs
0.6
0.4
µs
START set-up time
Input fall time
(1
400
Unit
Max
0.4
Input rise time
tWR
Min
1.3
Data in set-up time
tPOFF
Max
Clock pulse width low
Clock pulse width
high
Noise suppression
time(1)
Clock low to data out
valid
Time the bus must be
free before a new
transmission can
start(1)
START hold time
Data in hold time
tPUP
2.5-5.0 V
100
50
ns
0.9
0.55
µs
1.3
0.5
µs
0.6
0.25
µs
0.6
0.25
µs
0
0
µs
100
100
ns
(1)
(1)
0.3
0.3
µs
300
100
ns
STOP set-up time
0.6
0.25
µs
Date out hold time
Vcc slew rate at
power up
Time required after
VCC is stable before
the device can accept
commands
Minimum time at
Vcc=0V between
power cycles
Write cycle time
25oC, Page Mode,
3.3V
50
50
ns
0.1
50
0.1
50
V/ms
100
100
µs
500
500
ms
5
1,000,000
5
ms
Write
Cycles
Notes: 1. This Parameter is expected by characterization but are not fully screened by test.
2. AC Measurement conditions:
RL (Connects to Vcc): 1.3KΩ
Input Pulse Voltages: 0.3Vcc to 0.7Vcc
Input and output timing reference Voltages: 0.5Vcc
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page9
Fremont Micro Devices
24C256A
DC CHARACTERISTICS
Symbol
Parameter
Test Conditions
Min
Typical
Units
5.5
V
VCC1
24C××A supply VCC
ICC1
Supply read current
VCC @ 5.0V SCL = 100 kHz
0.4
1.0
mA
ICC2
Supply write current
VCC @ 5.0V SCL = 100 kHz
2.0
3.0
mA
ISB1
Supply current
VCC @ 1.8V, VIN = VCC or VSS
< 1.0
µA
ISB2
Supply current
VCC @ 2.5V, VIN = VCC or VSS
< 1.0
µA
ISB3
Supply current
VCC @ 5.0V, VIN = VCC or VSS
< 1.0
µA
IIL
VIN = VCC or VSS
3.0
µA
VIN = VCC or VSS
3.0
µA
VIL
Input leakage current
Output leakage
current
Input low level
VIH
Input high level
VOL2
Output low level
VOL1
Output low level
ILO
1.8
Max
-0.6
VCC×0.3
V
VCC + 0.5
V
VCC @ 3.0V, IOL = 2.1 mA
0.4
V
VCC @ 1.8V, IOL = 0.15 mA
0.4
V
VCC× 0.7
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page10
Fremont Micro Devices
24C256A
ORDERING INFORMATION
FT24CxxxA - x x x - x
Density
256: 256kbits
Packaging
B: Tube
T: Tape and Reel
Temp. Range
E: -40℃-85℃
HSF
R: RoHS
G: Green
Package
D: DIP8
S: SOP8
M: MSOP8
T: TSSOP8
N:UDFN
Density
Package
Temperature
Range
Vcc
HSF
Packaging
Ordering Code
DIP8
-40℃-85℃
1.8V-5.5V
RoHS
Green
Tube
Tube
Tube
Tape and Reel
Tube
Tape and Reel
Tube
Tape and Reel
Tube
Tape and Reel
Tube
Tape and Reel
Tube
Tape and Reel
Tape and Reel
Tape and Reel
FT24C256A-EDR-B
FT24C256A-EDG-B
FT24C256A-ESR-B
FT24C256A-ESR-T
FT24C256A-ESG-B
FT24C256A-ESG-T
FT24C256A-EMR-B
FT24C256A-EMR-T
FT24C256A-EMG-B
FT24C256A-EMG-T
FT24C256A-ETR-B
FT24C256A-ETR-T
FT24C256A-ETG-B
FT24C256A-ETG-T
FT24C256A-ENR-T
FT24C256A-ENG-T
RoHS
SOP8
-40℃-85℃
1.8V-5.5V
Green
RoHS
256kbits
MSOP8
-40℃-85℃
1.8V-5.5V
Green
RoHS
TSSOP8
-40℃-85℃
1.8V-5.5V
Green
UDFN
-40℃-85℃
© 2016 Fremont Micro Devices Inc.
1.8V-5.5V
RoHS
Green
DS24C256-A2-page11
Fremont Micro Devices
24C256A
DIP8 PACKAGE OUTLINE DIMENSIONS
Symbol
A
A1
A2
B
B1
C
D
E
E1
e
L
E2
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
3.710
0.510
3.200
0.380
4.310
0.146
0.020
0.126
0.015
0.170
3.600
0.570
1.524(BSC)
0.204
0.360
9.000
9.400
6.200
6.600
7.320
7.920
2.540 (BSC)
3.000
3.600
8.400
9.000
© 2016 Fremont Micro Devices Inc.
0.142
0.022
0.060(BSC)
0.008
0.014
0.354
0.370
0.244
0.260
0.288
0.312
0.100(BSC)
0.118
0.142
0.331
0.354
DS24C256-A2-page12
Fremont Micro Devices
24C256A
SOP8 PACKAGE OUTLINE DIMENSIONS
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
A
1.350
1.750
0.053
0.069
A1
0.100
0.250
0.004
0.010
A2
1.350
1.550
0.053
0.061
b
0.330
0.510
0.013
0.020
c
0.170
0.250
0.006
0.010
D
4.700
5.100
0.185
0.200
E
3.800
4.000
0.150
0.157
E1
5.800
6.200
0.228
0.244
e
1.270 (BSC)
0.050 (BSC)
L
0.400
1.270
0.016
0.050
θ
0°
8°
0°
8°
© 2016 Fremont Micro Devices Inc.
DS24C256-A2-page13
Fremont Micro Devices
24C256A
MSOP8 PACKAGE OUTLINE DIMENSIONS
Symbol
A
A1
A2
b
c
D
e
E
E1
L
θ
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
0.820
0.020
0.750
0.250
0.090
2.900
1.100
0.150
0.950
0.380
0.230
3.100
0.320
0.001
0.030
0.010
0.004
0.114
0.043
0.006
0.037
0.015
0.009
0.122
0.65 (BSC)
2.900
4.750
0.400
0°
© 2016 Fremont Micro Devices Inc.
0.026 (BSC)
3.100
5.050
0.800
6°
0.114
0.187
0.016
0°
0.122
0.199
0.031
6°
DS24C256-A2-page14
Fremont Micro Devices
24C256A
TSSOP8 PACKAGE OUTLINE DIMENSIONS
Symbol
D
E
b
c
E1
A
A2
A1
e
L
H
θ
Dimensions In Millimeters
Dimensions In Inches
Min
Max
Min
Max
2.900
4.300
0.190
0.090
6.250
3.100
4.500
0.300
0.200
6.550
1.100
1.000
0.150
0.114
0.169
0.007
0.004
0.246
0.122
0.177
0.012
0.008
0.258
0.043
0.039
0.006
0.800
0.020
0.031
0.001
0.65 (BSC)
0.500
0.026 (BSC)
0.700
0.020
0.25 (TYP)
1°
© 2016 Fremont Micro Devices Inc.
0.028
0.01 (TYP)
7°
1°
7°
DS24C256-A2-page15
Fremont Micro Devices
24C256A
UDFN8 PACKAGE OUTLINE DIMENSIONS
Symbol
A
A1
b
b1
c
D
D2
e
Nd
E
E2
L
h
© 2016 Fremont Micro Devices Inc.
Dimensions In Millimeters
Min
0.450
0.000
0.180
Max
0.550
0.050
0.300
0.160REF
0.100
0.200
1.900
2.100
1.400
1.600
0.500BSC
1.500BSC
2.900
3.100
1.500
1.700
0.300
0.500
0.200
0.300
Dimensions In Inches
Min
Max
0.017
0.021
0.000
0.002
0.007
0.039
0.006REF
0.004
0.008
0.075
0.083
0.055
0.062
0.020BSC
0.059BSC
0.114
0.122
0.059
0.067
0.012
0.020
0.066
0.12
DS24C256-A2-page16
Fremont Micro Devices
24C256A
Fremont Micro Devices (SZ) Limited
#5-8, 10/F, Changhong Building, Ke-Ji Nan 12 Road, Nanshan District, Shenzhen
Tel: (86 755) 86117811
Fax: (86 755) 86117810
Fremont Micro Devices (Hong Kong) Limited
#16, 16/F, Blk B, Veristrong Industrial Centre, 34-36 Au Pui Wan Street, Fotan, Shatin, Hong Kong
Tel: (852) 27811186
Fax: (852) 27811144
Web Site: http://www.fremontmicro.com/
* Information furnished is believed to be accurate and reliable. However, Fremont Micro Devices, Incorporated
(BVI) assumes no responsibility for the consequences of use of such information or for any infringement of
patents of other rights of third parties which may result from its use. No license is granted by implication or
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