2010 Microchip Technology Inc.
DS21191S-page 1
24AA128/24LC128/24FC128
Device Selection Table
Features:
• Single Supply with Operation down to 1.7V for
24AA128/24FC128 devices, 2.5V for 24LC128
Devices
• Low-Power CMOS Technology:
- Write current 3 mA, typical
- Standby current 100 nA, typical
• 2-Wire Serial Interface, I
2
C™ Compatible
• Cascadable up to Eight Devices
• Schmitt Trigger Inputs for Noise Suppression
• Output Slope Control to Eliminate Ground Bounce
• 100 kHz and 400 kHz Clock Compatibility
• 1 MHz Clock for FC Versions
• Page Write Time 5 ms, typical
• Self-Timed Erase/Write Cycle
• 64-Byte Page Write Buffer
• Hardware Write-Protect
• ESD Protection >4000V
• More than 1 Million Erase/Write Cycles
• Data Retention > 200 years
• Factory Programming Available
• Packages include 8-lead PDIP, SOIC, TSSOP,
DFN, TDFN, MSOP, and Chip Scale Packages
• Pb-Free and RoHS Compliant
• Temperature Ranges:
Description:
The Microchip Technology Inc. 24AA128/24LC128/
24FC128 (24XX128*) is a 16K x 8 (128 Kbit) Serial
Electrically Erasable PROM (EEPROM), capable of
operation across a broad voltage range (1.7V to 5.5V).
It has been developed for advanced, low-power
applications such as personal communications or data
acquisition. This device also has a page write capabil-
ity of up to 64 bytes of data. This device is capable of
both random and sequential reads up to the 128K
boundary. Functional address lines allow up to eight
devices on the same bus, for up to 1 Mbit address
space. This device is available in the standard 8-pin
plastic DIP, SOIC (3.90 mm and 5.28 mm), TSSOP,
MSOP, DFN, TDFN and Chip Scale packages.
Block Diagram
*24XX128 is used in this document as a generic part number
for the 24AA128/24LC128/24FC128 devices.
Package Types
Part
Number
V
CC
Range
Max. Clock
Frequency
Temp.
Ranges
24AA128
1.7-5.5V
400 kHz
(1)
I
24LC128
2.5-5.5V
400 kHz
I, E
24FC128
1.7-5.5V
1 MHz
(2)
I
Note 1:
100 kHz for V
CC
< 2.5V.
2:
400 kHz for V
CC
< 2.5V.
- Industrial (I):
-40
C to +85C
- Automotive (E):
-40
C to +125C
HV Generator
EEPROM
Array
Page Latches
YDEC
XDEC
Sense Amp.
R/W Control
M
emory
C
ontrol
L
ogic
I/O
C
ontrol
L
ogic
I/O
A0 A1 A2
SDA
SCL
V
CC
V
SS
WP
A0
A1
A2
V
SS
V
CC
WP
SCL
SDA
1
2
3
4
8
7
6
5
24
X
X
1
28
PDIP/SOIC
TSSOP/MSOP
1
A0
A1
A2
V
SS
1
2
3
4
8
7
6
5
V
CC
WP
SCL
SDA
2
4X
X
128
DFN/TDFN
A0
A1
A2
V
SS
WP
SCL
SDA
24
X
X
128
5
6
7
8
4
3
2
1
V
CC
Note 1: Pins A0 and A1 are no-connects for the MSOP package only.
CS (Chip Scale)
2
1
2
3
4
5
6
7
8
V
CC
A1 A0
WP
A2
SDA SCL V
SS
(TOP DOWN VIEW,
BALLS NOT VISIBLE)
2: Available in I-temp, “AA” only.
128K I
2
C
™
CMOS Serial EEPROM
24AA128/24LC128/24FC128
DS21191S-page 2
2010 Microchip Technology Inc.
1.0
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings
(†)
V
CC
.............................................................................................................................................................................6.5V
All inputs and outputs w.r.t. V
SS
......................................................................................................... -0.6V to V
CC
+1.0V
Storage temperature ...............................................................................................................................-65°C to +150°C
Ambient temperature with power applied................................................................................................-40°C to +125°C
ESD protection on all pins
4 kV
TABLE 1-1:
DC CHARACTERISTICS
† NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device. This is a stress rating only and functional operation of the device at those or any other conditions above those
indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.
DC CHARACTERISTICS
Electrical Characteristics:
Industrial (I):
V
CC
= +1.7V to 5.5V T
A
= -40°C to +85°C
Automotive (E):
V
CC
= +2.5V to 5.5V T
A
= -40°C to 125°C
Param.
No.
Sym.
Characteristic
Min.
Max.
Units
Conditions
—
A0, A1, A2, SCL, SDA and
WP pins:
—
—
—
—
D1
V
IH
High-level input voltage
0.7 V
CC
—
V
—
D2
V
IL
Low-level input voltage
—
0.3 V
CC
0.2 V
CC
V
V
V
CC
2.5V
V
CC
< 2.5V
D3
V
HYS
Hysteresis of Schmitt Trigger
inputs (SDA, SCL pins)
0.05 V
CC
—
V
V
CC
2.5V (Note 1)
D4
V
OL
Low-level output voltage
—
0.40
V
I
OL
= 3.0 mA @ V
CC
= 4.5V
I
OL
= 2.1 mA @ V
CC
= 2.5V
D5
I
LI
Input leakage current
—
±1
A
V
IN
= V
SS
or V
CC
, WP = V
SS
V
IN
= V
SS
or V
CC
, WP = V
CC
D6
I
LO
Output leakage current
—
±1
A
V
OUT
= V
SS
or V
CC
D7
C
IN
,
C
OUT
Pin capacitance
(all inputs/outputs)
—
10
pF
V
CC
= 5.0V (Note 1)
T
A
= 25°C, F
CLK
= 1 MHz
D8
I
CC
Read Operating current
—
400
A
V
CC
= 5.5V, SCL = 400 kHz
I
CC
Write
—
3
mA
V
CC
= 5.5V
D9
I
CCS
Standby current
—
1
A
T
A
= -40°C to +85°C
SCL = SDA = V
CC
= 5.5V
A0, A1, A2, WP = V
SS
—
5
A
T
A
= -40°C to 125°C
SCL = SDA = V
CC
= 5.5V
A0, A1, A2, WP = V
SS
Note 1: This parameter is periodically sampled and not 100% tested.
2010 Microchip Technology Inc.
DS21191S-page 3
24AA128/24LC128/24FC128
TABLE 1-2:
AC CHARACTERISTICS
AC CHARACTERISTICS
Electrical Characteristics:
Industrial (I):
V
CC
= +1.7V to 5.5V T
A
= -40°C to +85°C
Automotive (E):
V
CC
= +2.5V to 5.5V T
A
= -40°C to 125°C
Param.
No.
Sym.
Characteristic
Min.
Max.
Units
Conditions
1
F
CLK
Clock frequency
—
—
—
—
100
400
400
1000
kHz
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5V
V
CC
5.5V 24FC128
2
T
HIGH
Clock high time
4000
600
600
500
—
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5V
V
CC
5.5V 24FC128
3
T
LOW
Clock low time
4700
1300
1300
500
—
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5V
V
CC
5.5V 24FC128
4
T
R
SDA and SCL rise time
(Note 1)
—
—
—
1000
300
300
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
5.5V 24FC128
5
T
F
SDA and SCL fall time
(Note 1)
—
—
300
100
ns
All except, 24FC128
1.7V
V
CC
5.5V 24FC128
6
T
HD
:
STA
Start condition hold time
4000
600
600
250
—
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5V
V
CC
5.5V 24FC128
7
T
SU
:
STA
Start condition setup time
4700
600
600
250
—
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5V
V
CC
5.5V 24FC128
8
T
HD
:
DAT
Data input hold time
0
—
ns
(Note 2)
9
T
SU
:
DAT
Data input setup time
250
100
100
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
5.5V 24FC128
10
T
SU
:
STO
Stop condition setup time
4000
600
600
250
—
—
—
—
ns
1.7 V
V
CC
2.5V
2.5 V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5 V
V
CC
5.5V 24FC128
11
T
SU
:
WP
WP setup time
4000
600
600
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
5.5V 24FC128
12
T
HD
:
WP
WP hold time
4700
1300
1300
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
5.5V 24FC128
Note 1: Not 100% tested. C
B
= total capacitance of one bus line in pF.
2: As a transmitter, the device must provide an internal minimum delay time to bridge the undefined region
(minimum 300 ns) of the falling edge of SCL to avoid unintended generation of Start or Stop conditions.
3: The combined T
SP
and V
HYS
specifications are due to new Schmitt Trigger inputs, which provide improved
noise spike suppression. This eliminates the need for a T
I
specification for standard operation.
4: This parameter is not tested but ensured by characterization. For endurance estimates in a specific
application, please consult the Total Endurance™ Model, which can be obtained from Microchip’s web site
at www.microchip.com.
24AA128/24LC128/24FC128
DS21191S-page 4
2010 Microchip Technology Inc.
FIGURE 1-1:
BUS TIMING DATA
13
T
AA
Output valid from clock
(Note 2)
—
—
—
—
3500
900
900
400
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5V
V
CC
5.5V 24FC128
14
T
BUF
Bus free time: Time the bus
must be free before a new
transmission can start
4700
1300
1300
500
—
—
—
—
ns
1.7V
V
CC
2.5V
2.5V
V
CC
5.5V
1.7V
V
CC
2.5V 24FC128
2.5V
V
CC
5.5V 24FC128
15
T
OF
Output fall time from V
IH
minimum to V
IL
maximum
C
B
100 pF
10 + 0.1C
B
250
250
ns
All except, 24FC128 (Note 1)
24FC128 (Note 1)
16
T
SP
Input filter spike suppression
(SDA and SCL pins)
—
50
ns
All except, 24FC128 (Notes 1
and 3)
17
T
WC
Write cycle time (byte or
page)
—
5
ms
—
18
—
Endurance
1,000,000
—
cycles Page Mode, 25°C, 5.5V (Note 4)
TABLE 1-2:
AC CHARACTERISTICS (CONTINUED)
AC CHARACTERISTICS
Electrical Characteristics:
Industrial (I):
V
CC
= +1.7V to 5.5V T
A
= -40°C to +85°C
Automotive (E):
V
CC
= +2.5V to 5.5V T
A
= -40°C to 125°C
Param.
No.
Sym.
Characteristic
Min.
Max.
Units
Conditions
Note 1: Not 100% tested. C
B
= total capacitance of one bus line in pF.
2: As a transmitter, the device must provide an internal minimum delay time to bridge the undefined region
(minimum 300 ns) of the falling edge of SCL to avoid unintended generation of Start or Stop conditions.
3: The combined T
SP
and V
HYS
specifications are due to new Schmitt Trigger inputs, which provide improved
noise spike suppression. This eliminates the need for a T
I
specification for standard operation.
4: This parameter is not tested but ensured by characterization. For endurance estimates in a specific
application, please consult the Total Endurance™ Model, which can be obtained from Microchip’s web site
at www.microchip.com.
(unprotected)
(protected)
SCL
SDA
IN
SDA
OUT
WP
5
7
6
16
3
2
8
9
13
D3
4
10
11
12
14
2010 Microchip Technology Inc.
DS21191S-page 5
24AA128/24LC128/24FC128
2.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 2-1.
TABLE 2-1:
PIN FUNCTION TABLE
2.1
A0, A1, A2 Chip Address Inputs
The A0, A1 and A2 inputs are used by the 24XX128 for
multiple device operations. The levels on these inputs
are compared with the corresponding bits in the slave
address. The chip is selected if the compare is true.
For the MSOP package only, pins A0 and A1 are not
connected.
Up to eight devices (two for the MSOP package) may
be connected to the same bus by using different Chip
Select bit combinations. These inputs must be
connected to either V
CC
or V
SS
.
In most applications, the chip address inputs A0, A1
and A2 are hard-wired to logic ‘0’ or logic ‘1’. For
applications in which these pins are controlled by a
microcontroller or other programmable device, the chip
address pins must be driven to logic ‘0’ or logic ‘1’
before normal device operation can proceed.
2.2
Serial Data (SDA)
This is a bidirectional pin used to transfer addresses
and data into and out of the device. It is an open drain
terminal. Therefore, the SDA bus requires a pull-up
resistor to V
CC
(typical 10 k
for 100 kHz, 2 k for
400 kHz and 1 MHz).
For normal data transfer, SDA is allowed to change
only during SCL low. Changes during SCL high are
reserved for indicating the Start and Stop conditions.
2.3
Serial Clock (SCL)
This input is used to synchronize the data transfer to
and from the device.
2.4
Write-Protect (WP)
This pin must be connected to either V
SS
or V
CC
. If tied
to V
SS
, write operations are enabled. If tied to V
CC
,
write operations are inhibited but read operations are
not affected.
3.0
FUNCTIONAL DESCRIPTION
The 24XX128 supports a bidirectional 2-wire bus and
data transmission protocol. A device that sends data
onto the bus is defined as a transmitter and a device
receiving data as a receiver. The bus must be
controlled by a master device which generates the
Serial Clock (SCL), controls the bus access and
generates the Start and Stop conditions while the
24XX128 works as a slave. Both master and slave can
operate as a transmitter or receiver, but the master
device determines which mode is activated.
Name
PDIP
SOIC
TSSOP
MSOP
DFN
(1)
TDFN
(1)
CS
Function
A0
1
1
1
—
1
1
3
User Configurable Chip Select
A1
2
2
2
—
2
2
2
User Configurable Chip Select
(NC)
—
—
—
1, 2
—
—
—
Not Connected
A2
3
3
3
3
3
3
5
User Configurable Chip Select
V
SS
4
4
4
4
4
4
8
Ground
SDA
5
5
5
5
5
5
6
Serial Data
SCL
6
6
6
6
6
6
7
Serial Clock
WP
7
7
7
7
7
7
4
Write-Protect Input
V
CC
8
8
8
8
8
8
1
+1.7V to 5.5V (24AA128)
+2.5V to 5.5V (24LC128)
+1.7V to 5.5V (24FC128)
Note 1:
The exposed pad on the DFN/TDFN package can be connected to V
SS
or left floating.
24AA128/24LC128/24FC128
DS21191S-page 6
2010 Microchip Technology Inc.
4.0
BUS CHARACTERISTICS
The following bus protocol has been defined:
• Data transfer may be initiated only when the bus
is not busy.
• During data transfer, the data line must remain
stable whenever the clock line is high. Changes in
the data line while the clock line is high will be
interpreted as a Start or Stop condition.
Accordingly, the following bus conditions have been
defined (Figure 4-1).
4.1
Bus Not Busy (A)
Both data and clock lines remain high.
4.2
Start Data Transfer (B)
A high-to-low transition of the SDA line while the clock
(SCL) is high determines a Start condition. All
commands must be preceded by a Start condition.
4.3
Stop Data Transfer (C)
A low-to-high transition of the SDA line, while the clock
(SCL) is high, determines a Stop condition. All
operations must end with a Stop condition.
4.4
Data Valid (D)
The state of the data line represents valid data when,
after a Start condition, the data line is stable for the
duration of the high period of the clock signal.
The data on the line must be changed during the low
period of the clock signal. There is one bit of data per
clock pulse.
Each data transfer is initiated with a Start condition and
terminated with a Stop condition. The number of the
data bytes transferred between the Start and Stop
conditions is determined by the master device.
4.5
Acknowledge
Each receiving device, when addressed, is obliged to
generate an Acknowledge signal after the reception of
each byte. The master device must generate an extra
clock pulse, which is associated with this Acknowledge
bit.
A device that acknowledges must pull down the SDA
line during the acknowledge clock pulse in such a way
that the SDA line is stable low during the high period of
the acknowledge related clock pulse. Of course, setup
and hold times must be taken into account. During
reads, a master must signal an end of data to the slave
by NOT generating an Acknowledge bit on the last byte
that has been clocked out of the slave. In this case, the
slave (24XX128) will leave the data line high to enable
the master to generate the Stop condition.
FIGURE 4-1:
DATA TRANSFER SEQUENCE ON THE SERIAL BUS
FIGURE 4-2:
ACKNOWLEDGE TIMING
Note:
The 24XX128 does not generate any
Acknowledge bits if an internal
programming cycle is in progress.
Address or
Acknowledge
Valid
Data
Allowed
to Change
Stop
Condition
Start
Condition
SCL
SDA
(A)
(B)
(D)
(D)
(C)
(A)
SCL
9
8
7
6
5
4
3
2
1
1
2
3
Transmitter must release the SDA line at this point,
allowing the Receiver to pull the SDA line low to
acknowledge the previous eight bits of data.
Receiver must release the SDA line
at this point so the Transmitter can
continue sending data.
Data from transmitter
SDA
Acknowledge
Bit
Data from transmitter
2010 Microchip Technology Inc.
DS21191S-page 7
24AA128/24LC128/24FC128
5.0
DEVICE ADDRESSING
A control byte is the first byte received following the
Start condition from the master device (Figure 5-1).
The control byte consists of a 4-bit control code. For the
24XX128, this is set as ‘1010
’
binary for read and write
operations. The next three bits of the control byte are
the Chip Select bits (A2, A1, A0). The Chip Select bits
allow the use of up to eight 24XX128 devices on the
same bus and are used to select which device is
accessed. The Chip Select bits in the control byte must
correspond to the logic levels on the corresponding A2,
A1 and A0 pins for the device to respond. These bits
are, in effect, the three Most Significant bits of the word
address.
For the MSOP package, the A0 and A1 pins are not
connected. During device addressing, the A0 and A1
Chip Select bits (Figures 5-1 and 5-2) should be set to
‘0’. Only two 24XX128 MSOP packages can be
connected to the same bus.
The last bit of the control byte defines the operation to
be performed. When set to a one, a read operation is
selected. When set to a zero, a write operation is
selected. The next two bytes received define the
address of the first data byte (Figure 5-2). Because
only A13…A0 are used, the upper two address bits are
“don’t care” bits. The upper address bits are transferred
first, followed by the Less Significant bits.
Following the Start condition, the 24XX128 monitors
the SDA bus checking the device type identifier being
transmitted. Upon receiving a ‘1010
’
code and
appropriate device select bits, the slave device outputs
an Acknowledge signal on the SDA line. Depending on
the state of the R/W bit, the 24XX128 will select a read
or write operation.
FIGURE 5-1:
CONTROL BYTE
FORMAT
5.1
Contiguous Addressing Across
Multiple Devices
The Chip Select bits A2, A1 and A0 can be used to
expand the contiguous address space for up to 1 Mbit
by adding up to eight 24XX128 devices on the same
bus. In this case, software can use A0 of the control
byte as address bit A14; A1 as address bit A15; and A2
as address bit A16. It is not possible to sequentially
read across device boundaries.
For the MSOP package, up to two 24XX128 devices
can be added for up to 256 Kbit of address space. In
this case, software can use A2 of the control byte as
address bit A16. Bits A0 (A14) and A1 (A15) of the
control byte must always be set to logic ‘0’ for the
MSOP.
FIGURE 5-2:
ADDRESS SEQUENCE BIT ASSIGNMENTS
1
0
1
0
A2
A1
A0
S
ACK
R/W
Control Code
Chip Select
Bits
Slave Address
Acknowledge Bit
Start Bit
Read/Write Bit
1
0
1
0
A
2
A
1
A
0 R/W
x
x
A
11
A
10
A
9
A
7
A
0
A
8
•
•
•
•
•
•
A
12
Control Byte
Address High Byte
Address Low Byte
Control
Code
Chip
Select
Bits
x = “don’t care” bit
A
13
24AA128/24LC128/24FC128
DS21191S-page 8
2010 Microchip Technology Inc.
6.0
WRITE OPERATIONS
6.1
Byte Write
Following the Start condition from the master, the
control code (four bits), the Chip Select (three bits) and
the R/W bit (which is a logic low) are clocked onto the
bus by the master transmitter. This indicates to the
addressed slave receiver that the address high byte will
follow after it has generated an Acknowledge bit during
the ninth clock cycle. Therefore, the next byte
transmitted by the master is the high-order byte of the
word address and will be written into the Address
Pointer of the 24XX128. The next byte is the Least
Significant Address Byte. After receiving another
Acknowledge signal from the 24XX128, the master
device will transmit the data word to be written into the
addressed memory location. The 24XX128 acknowl-
edges again and the master generates a Stop
condition. This initiates the internal write cycle and
during this time, the 24XX128 will not generate
Acknowledge signals (Figure 6-1). If an attempt is
made to write to the array with the WP pin held high, the
device will acknowledge the command, but no write
cycle will occur, no data will be written, and the device
will immediately accept a new command. After a byte
Write command, the internal address counter will point
to the address location following the one that was just
written.
6.2
Page Write
The write control byte, word address, and the first data
byte are transmitted to the 24XX128 in much the same
way as in a byte write. The exception is that instead of
generating a Stop condition, the master transmits up to
63 additional bytes, which are temporarily stored in the
on-chip page buffer, and will be written into memory
once the master has transmitted a Stop condition.
Upon receipt of each word, the six lower Address
Pointer bits are internally incremented by ‘
1
’. If the
master should transmit more than 64 bytes prior to
generating the Stop condition, the address counter will
roll over and the previously received data will be over-
written. As with the byte write operation, once the Stop
condition is received, an internal write cycle will begin
(Figure 6-2). If an attempt is made to write to the array
with the WP pin held high, the device will acknowledge
the command, but no write cycle will occur, no data will
be written and the device will immediately accept a new
command.
6.3
Write Protection
The WP pin allows the user to write-protect the entire
array (0000-3FFF) when the pin is tied to V
CC
. If tied to
V
SS
the write protection is disabled. The WP pin is
sampled at the Stop bit for every Write command
(Figure 1-1). Toggling the WP pin after the Stop bit will
have no effect on the execution of the write cycle.
Note:
When doing a write of less than 64 bytes
the data in the rest of the page is refreshed
along with the data bytes being written.
This will force the entire page to endure a
write cycle, for this reason endurance is
specified per page.
Note:
Page write operations are limited to
writing bytes within a single physical
page, regardless of the number of
bytes actually being written. Physical
page boundaries start at addresses
that are integer multiples of the page
buffer size (or ‘page size’) and end at
addresses that are integer multiples of
[page size – 1]. If a Page Write
command attempts to write across a
physical page boundary, the result is
that the data wraps around to the
beginning of the current page (over-
writing data previously stored there),
instead of being written to the next
page, as might be expected. It is,
therefore, necessary for the applica-
tion software to prevent page write
operations that would attempt to cross
a page boundary.
2010 Microchip Technology Inc.
DS21191S-page 9
24AA128/24LC128/24FC128
FIGURE 6-1:
BYTE WRITE
FIGURE 6-2:
PAGE WRITE
7.0
ACKNOWLEDGE POLLING
Since the device will not acknowledge during a write
cycle, this can be used to determine when the cycle is
complete (This feature can be used to maximize bus
throughput). Once the Stop condition for a Write
command has been issued from the master, the device
initiates the internally timed write cycle. ACK polling
can be initiated immediately. This involves the master
sending a Start condition, followed by the control byte
for a Write command (R/W = 0). If the device is still
busy with the write cycle, then no ACK will be returned.
If no ACK is returned, the Start bit and control byte must
be resent. If the cycle is complete, then the device will
return the ACK and the master can then proceed with
the next Read or Write command. See Figure 7-1 for
flow diagram.
FIGURE 7-1:
ACKNOWLEDGE
POLLING FLOW
x x
Bus Activity
Master
SDA Line
Bus Activity
S
T
A
R
T
Control
Byte
Address
High Byte
Address
Low Byte
Data
S
T
O
P
A
C
K
A
C
K
A
C
K
A
C
K
x = “don’t care” bit
S 1 0 1 0
0
A
2
A
1
A
0
P
x x
Bus Activity
Master
SDA Line
Bus Activity
S
T
A
R
T
Control
Byte
Address
High Byte
Address
Low Byte
Data Byte 0
S
T
O
P
A
C
K
A
C
K
A
C
K
A
C
K
Data Byte 63
A
C
K
x = “don’t care” bit
S 1 0 1 0
0
A
2
A
1
A
0
P
Send
Write Command
Send Stop
Condition to
Initiate Write Cycle
Send Start
Send Control Byte
with R/W = 0
Did Device
Acknowledge
(ACK = 0)?
Next
Operation
No
Yes
24AA128/24LC128/24FC128
DS21191S-page 10
2010 Microchip Technology Inc.
8.0
READ OPERATION
Read operations are initiated in much the same way as
write operations with the exception that the R/W bit of
the control byte is set to ‘
1
’. There are three basic types
of read operations: current address read, random read
and sequential read.
8.1
Current Address Read
The 24XX128 contains an address counter that main-
tains the address of the last word accessed, internally
incremented by ‘
1
’. Therefore, if the previous read
access was to address ‘
n
’ (
n
is any legal address), the
next current address read operation would access data
from address
n + 1
.
Upon receipt of the control byte with R/W bit set to ‘
1
’,
the 24XX128 issues an acknowledge and transmits the
8-bit data word. The master will not acknowledge the
transfer, but does generate a Stop condition and the
24XX128 discontinues transmission (Figure 8-1).
FIGURE 8-1:
CURRENT ADDRESS
READ
8.2
Random Read
Random read operations allow the master to access
any memory location in a random manner. To perform
this type of read operation, the word address must first
be set. This is done by sending the word address to the
24XX128 as part of a write operation (R/W bit set to
‘
0’
). Once the word address is sent, the master gener-
ates a Start condition following the acknowledge. This
terminates the write operation, but not before the inter-
nal Address Pointer is set. The master then issues the
control byte again, but with the R/W bit set to a ‘
1
’. The
24XX128 will then issue an acknowledge and transmit
the 8-bit data word. The master will not acknowledge
the transfer but does generate a Stop condition, which
causes the 24XX128 to discontinue transmission
(Figure 8-2). After a random Read command, the
internal address counter will point to the address
location following the one that was just read.
8.3
Sequential Read
Sequential reads are initiated in the same way as a
random read except that after the 24XX128 transmits
the first data byte, the master issues an acknowledge
as opposed to the Stop condition used in a random
read. This acknowledge directs the 24XX128 to
transmit the next sequentially addressed 8-bit word
(Figure 8-3). Following the final byte transmitted to the
master, the master will NOT generate an acknowledge
but will generate a Stop condition. To provide
sequential reads, the 24XX128 contains an internal
Address Pointer which is incremented by one at the
completion of each operation. This Address Pointer
allows the entire memory contents to be serially read
during one operation. The internal Address Pointer will
automatically roll over from address 3FFF to address
0000
if the master acknowledges the byte received
from the array address 3FFF.
FIGURE 8-2:
RANDOM READ
FIGURE 8-3:
SEQUENTIAL READ
Bus
Activity
Master
SDA Line
Bus Activity
P
S
S
T
O
P
Control
Byte
S
T
A
R
T
Data
A
C
K
N
O
A
C
K
1
1
0
0 A A A 1
Byte
2 1 0
x x
Bus Activity
Master
SDA Line
Bus Activity
A
C
K
N
O
A
C
K
A
C
K
A
C
K
A
C
K
S
T
O
P
S
T
A
R
T
Control
Byte
Address
High Byte
Address
Low Byte
Control
Byte
Data
Byte
S
T
A
R
T
x = “don’t care” bit
S 1 0 1 0 A A A 0
2 1 0
S 1 0 1 0 A A A
1
2 1 0
P
Bus Activity
Master
SDA Line
Bus Activity
Control
Byte
Data (n)
Data (n + 1)
Data (n + 2)
Data (n + x)
N
O
A
C
K
A
C
K
A
C
K
A
C
K
A
C
K
S
T
O
P
P