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M24C32-RMB6TP |M24C32RMB6TPSTN/a1098avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32-RMN6P |M24C32RMN6PSTN/a3820avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32-RMN6TP |M24C32RMN6TPSTMN/a1840avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32MW6TSTN/a2336avai64/32 Kbit Serial IC Bus EEPROM
M24C32-RDW6TP |M24C32RDW6TPSTN/a160350avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32-RMB6T |M24C32RMB6TSTN/a659avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32WBN6PSTN/a100avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32-WBN6P |M24C32WBN6PSTN/a5000avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32-WBN6P |M24C32WBN6PSTMN/a10000avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32-WBN6P |M24C32WBN6PST,STN/a10000avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32-WDW6TP |M24C32WDW6TPSTN/a12000avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C32WMN6TSTN/a1800avai64/32 Kbit Serial IC Bus EEPROM
M24C32WMN6-T |M24C32WMN6TSTN/a224avai64/32 Kbit Serial IC Bus EEPROM
M24C32WMW6TSTN/a260avai64/32 Kbit Serial IC Bus EEPROM
M24C64-MN6TP |M24C64MN6TPSTN/a269avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C64MW6TSTN/a601avai64/32 Kbit Serial IC Bus EEPROM
M24C64-RDW6T |M24C64RDW6TSTN/a5190avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C64-RDW6TP |M24C64RDW6TPSTN/a50000avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C64-RMN6TP |M24C64RMN6TPSTN/a65434avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C64-WBN6P |M24C64WBN6PSTN/a4560avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C64-WBN6T |M24C64WBN6TSTN/a16avai64Kbit and 32Kbit Serial IC Bus EEPROM
M24C64WMN6TSTN/a4000avai64/32 Kbit Serial IC Bus EEPROM
M24C64WMW6TSTN/a11697avai64/32 Kbit Serial IC Bus EEPROM
24C64N/a186avai2-WireSerialEEPROM


M24C32-RDW6TP ,64Kbit and 32Kbit Serial IC Bus EEPROMAbsolute Maximum Ratings . . . . . . . 14DC AND AC PARAMETERS . 15Table 8. Operating Cond ..
M24C32-RMB6T ,64Kbit and 32Kbit Serial IC Bus EEPROMBlock Diagram . . 7DEVICE OPERATION . . . . . . . 8Start Condition . 8Stop Con ..
M24C32-RMB6TP ,64Kbit and 32Kbit Serial IC Bus EEPROMLogic Diagram . . 4Table 2. Signal Names . . 4Power On Reset: VCC Lock-Out Write Prot ..
M24C32-RMN6P ,64Kbit and 32Kbit Serial IC Bus EEPROMFEATURES SUMMARY2■ Two-Wire I C Serial Interface Figure 1. PackagesSupports 400kHz Protocol■ Single ..
M24C32-RMN6TP ,64Kbit and 32Kbit Serial IC Bus EEPROMM24C64M24C3264Kbit and 32Kbit Serial I²C Bus EEPROM
M24C32-WBN6 ,64Kbit and 32Kbit Serial IC Bus EEPROMLogic Diagram SCL Serial ClockWC Write ControlVCCV Supply VoltageCCV GroundSS3Power On Reset: V Loc ..
M38067MC-078FP , SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
M38067MC-078FP , SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
M38067MC-204FP , SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
M38067MC-204FP , SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
M38067MC-377FP , SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
M38067MC-377FP , SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER


24C64-M24C32MW6T-M24C32-RDW6TP-M24C32-RMB6T-M24C32-RMB6TP-M24C32-RMN6P-M24C32-RMN6TP-M24C32WBN6P-M24C32-WBN6P-M24C32-WDW6TP-M24C32WMN6T-M24C32WMN6-T-M24C32WMW6T-M24C64-MN6TP-M24C64MW6T-M24C64-RDW6T-M24C64-RDW6TP-M24C64-RMN6TP-M24C64-WBN6P-M24C64-WBN6T-M24C
2-WireSerialEEPROM
1/26January 2005
M24C64
M24C32

64Kbit and 32Kbit Serial I²C Bus EEPROM
FEATURES SUMMARY
Two-Wire I2 C Serial Interface
Supports 400kHz Protocol Single Supply Voltage: 4.5 to 5.5V for M24Cxx 2.5 to 5.5V for M24Cxx-W 1.8 to 5.5V for M24Cxx-R Write Control Input BYTE and PAGE WRITE (up to 32 Bytes) RANDOM and SEQUENTIAL READ Modes Self-Timed Programming Cycle Automatic Address Incrementing Enhanced ESD/Latch-Up Protection More than 1 Million Erase/Write Cycles More than 40-Year Data Retention
Table 1. Product List
M24C64, M24C32
TABLE OF CONTENTS
FEATURES SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Table 1. Product List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Figure 1. Packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
SUMMARY DESCRIPTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Figure 2. Logic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Table 2. Signal Names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Power On Reset: VCC Lock-Out Write Protect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Figure 3. DIP, SO, TSSOP and UFDFPN Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
SIGNAL DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Serial Clock (SCL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Serial Data (SDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Chip Enable (E0, E1, E2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Write Control (WC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Figure 4. Maximum RL Value versus Bus Capacitance (CBUS) for an I2 C Bus . . . . . . . . . . . . . . . .5
Figure 5.I2 C Bus Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Table 3. Device Select Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Table 4. Most Significant Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Table 5. Least Significant Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
MEMORY ORGANIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Figure 6. Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
DEVICE OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Start Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Stop Condition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Acknowledge Bit (ACK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Data Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Memory Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Table 6. Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Figure 7. Write Mode Sequences with WC=1 (data write inhibited) . . . . . . . . . . . . . . . . . . . . . . . . .9
Write Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Byte Write. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Page Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Figure 8. Write Mode Sequences with WC=0 (data write enabled) . . . . . . . . . . . . . . . . . . . . . . . .10
Figure 9. Write Cycle Polling Flowchart using ACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Minimizing System Delays by Polling On ACK. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Figure 10.Read Mode Sequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Read Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Random Address Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Current Address Read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Sequential Read. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
3/26
M24C64, M24C32
Acknowledge in Read Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
INITIAL DELIVERY STATE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
MAXIMUM RATING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Table 7. Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
DC AND AC PARAMETERS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Table 8. Operating Conditions (M24Cxx-6). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Table 9. Operating Conditions (M24Cxx-W) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Table 10. Operating Conditions (M24Cxx-R). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Table 11. AC Measurement Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Figure 11.AC Measurement I/O Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Table 12. Input Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Table 13. DC Characteristics (M24Cxx(1) , M24Cxx-W6 and M24Cxx-W3). . . . . . . . . . . . . . . . . . .16
Table 14. DC Characteristics (M24Cxx-W6 and M24Cxx-W3) . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Table 15. DC Characteristics (M24Cxx-R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Table 16. AC Characteristics (M24Cxx-6, M24Cxx-W6 and M24Cxx-W3) . . . . . . . . . . . . . . . . . . .18
Table 17. AC Characteristics (M24Cxx-R). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Figure 12.AC Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
PACKAGE MECHANICAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Figure 13.PDIP8 – 8 pin Plastic DIP, 0.25mm lead frame, Package Outline . . . . . . . . . . . . . . . . .20
Table 18. PDIP8 – 8 pin Plastic DIP, 0.25mm lead frame, Package Mechanical Data . . . . . . . . . .20
Figure 14.SO8 narrow – 8 lead Plastic Small Outline, 150 mils body width, Package Outline . . . .21
Table 19. SO8 narrow – 8 lead Plastic Small Outline, 150 mils body width,
Package Mechanical Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Figure 15.TSSOP8 – 8 lead Thin Shrink Small Outline, Package Outline . . . . . . . . . . . . . . . . . . .22
Table 20. TSSOP8 – 8 lead Thin Shrink Small Outline, Package Mechanical Data . . . . . . . . . . . .22
Figure 16.UFDFPN8 (MLP8) – 8-lead Ultra thin Fine pitch Dual Flat Package No lead 2x3mm. . .23
Table 21. UFDFPN8 (MLP8) – 8-lead Ultra thin Fine pitch Dual Flat Package No lead 2x3mm,
Package Mechanical Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
PART NUMBERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Table 22. Ordering Information Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
REVISION HISTORY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Table 23. Document Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
M24C64, M24C32
SUMMARY DESCRIPTION
5/26
M24C64, M24C32
SIGNAL DESCRIPTION
Serial Clock (SCL).
This input signal is used to
strobe all data in and out of the device. In applica-
tions where this signal is used by slave devices to
synchronize the bus to a slower clock, the bus
master must have an open drain output, and a
pull-up resistor must be connected from Serial
Clock (SCL) to VCC. (Figure 4. indicates how the
value of the pull-up resistor can be calculated). In
most applications, though, this method of synchro-
nization is not employed, and so the pull-up resis-
tor is not necessary, provided that the bus master
has a push-pull (rather than open drain) output.
Serial Data (SDA).
This bi-directional signal is
used to transfer data in or out of the device. It is an
open drain output that may be wire-OR’ed with
other open drain or open collector signals on the
bus. A pull up resistor must be connected from Se-
rial Data (SDA) to VCC. (Figure 4. indicates how
the value of the pull-up resistor can be calculated).
Chip Enable (E0, E1, E2).
These input signals
are used to set the value that is to be looked for on
the three least significant bits (b3, b2, b1) of the 7-
bit Device Select Code. These inputs must be tied
to VCC or VSS, to establish the Device Select
Code.
Write Control (WC).
This input signal is useful
for protecting the entire contents of the memory
from inadvertent write operations. Write opera-
tions are disabled to the entire memory array when
Write Control (WC) is driven High. When uncon-
nected, the signal is internally read as VIL, and
Write operations are allowed.
When Write Control (WC) is driven High, Device
Select and Address bytes are acknowledged,
Data bytes are not acknowledged.
M24C64, M24C32
Table 4. Most Significant Byte Table 5. Least Significant Byte
7/26
M24C64, M24C32
MEMORY ORGANIZATION

The memory is organized as shown in Figure 6..
M24C64, M24C32
DEVICE OPERATION

The device supports the I2 C protocol. This is sum-
marized in Figure 5.. Any device that sends data
on to the bus is defined to be a transmitter, and
any device that reads the data to be a receiver.
The device that controls the data transfer is known
as the bus master, and the other as the slave de-
vice. A data transfer can only be initiated by the
bus master, which will also provide the serial clock
for synchronization. The M24Cxx device is always
a slave in all communication.
Start Condition

Start is identified by a falling edge of Serial Data
(SDA) while Serial Clock (SCL) is stable in the
High state. A Start condition must precede any
data transfer command. The device continuously
monitors (except during a Write cycle) Serial Data
(SDA) and Serial Clock (SCL) for a Start condition,
and will not respond unless one is given.
Stop Condition

Stop is identified by a rising edge of Serial Data
(SDA) while Serial Clock (SCL) is stable and driv-
en High. A Stop condition terminates communica-
tion between the device and the bus master. A
Read command that is followed by NoAck can be
followed by a Stop condition to force the device
into the Stand-by mode. A Stop condition at the
end of a Write command triggers the internal Write
cycle.
Acknowledge Bit (ACK)

The acknowledge bit is used to indicate a success-
ful byte transfer. The bus transmitter, whether it be
bus master or slave device, releases Serial Data
(SDA) after sending eight bits of data. During theth clock pulse period, the receiver pulls Serial
Data (SDA) Low to acknowledge the receipt of the
eight data bits.
Data Input

During data input, the device samples Serial Data
(SDA) on the rising edge of Serial Clock (SCL).
For correct device operation, Serial Data (SDA)
must be stable during the rising edge of Serial
Clock (SCL), and the Serial Data (SDA) signal
must change only when Serial Clock (SCL) is driv-
en Low.
Memory Addressing

To start communication between the bus master
and the slave device, the bus master must initiate
a Start condition. Following this, the bus master
sends the Device Select Code, shown in Table 3.
(on Serial Data (SDA), most significant bit first).
The Device Select Code consists of a 4-bit Device
Type Identifier, and a 3-bit Chip Enable “Address”
(E2, E1, E0). To address the memory array, the 4-
bit Device Type Identifier is 1010b.
Up to eight memory devices can be connected on
a single I2 C bus. Each one is given a unique 3-bit
code on the Chip Enable (E0, E1, E2) inputs.
When the Device Select Code is received, the de-
vice only responds if the Chip Enable Address is
the same as the value on the Chip Enable (E0, E1,
E2) inputs.
The 8th bit is the Read/Write bit (RW). This bit is
set to 1 for Read and 0 for Write operations.
If a match occurs on the Device Select code, the
corresponding device gives an acknowledgment
on Serial Data (SDA) during the 9th bit time. If the
device does not match the Device Select code, it
deselects itself from the bus, and goes into Stand-
by mode.
Table 6. Operating Modes

Note:1. X = VIH or VIL.
9/26
M24C64, M24C32
Write Operations

Following a Start condition the bus master sends
a Device Select Code with the Read/Write bit
(RW) reset to 0. The device acknowledges this, as
shown in Figure 8., and waits for two address
bytes. The device responds to each address byte
with an acknowledge bit, and then waits for the
data byte.
Writing to
Control (WC) is driven High. Any Write instruction
with Write Control (WC) driven High (during a pe-
riod of time from the Start condition until the end of
the two address bytes) will not modify the memory
contents, and the accompanying data bytes are
not acknowledged, as shown in Figure 7..
Each data byte in the memory has a 16-bit (two
byte wide) address. The Most Significant Byte (Ta-
ble 4.) is sent first, followed by the Least Signifi-
cant Byte (Table 5.). Bits b15 to b0 form the
address of the byte in memory.
When the bus master generates a Stop condition
immediately after the Ack bit (in the “10th bit” time
slot), either at the end of a Byte Write or a Page
Write, the internal Write cycle is triggered. A Stop
condition at any other time slot does not trigger the
internal Write cycle.
After the Stop condition, the delay tW, and the suc-
cessful completion of a Write operation, the de-
vice’s internal address counter is incremented
automatically, to point to the next byte address af-
ter the last one that was modified.
During the internal Write cycle, Serial Data (SDA)
is disabled internally, and the device does not re-
spond to any requests.
Byte Write

After the Device Select code and the address
bytes, the bus master sends one data byte. If the
addressed location is Write-protected, by Write
Control (WC) being driven High, the device replies
with NoAck, and the location is not modified. If, in-
stead, the addressed location is not Write-protect-
ed, the device replies with Ack. The bus master
terminates the transfer by generating a Stop con-
dition, as shown in Figure 8..
M24C64, M24C32
Page Write

The Page Write mode allows up to 32 bytes to be
written in a single Write cycle, provided that they
are all located in the same ’row’ in the memory:
that is, the most significant memory address bits
(b12-b5 for M24C64, and b11-b5 for M24C32) are
the same. If more bytes are sent than will fit up to
the end of the row, a condition known as ‘roll-over’
occurs. This should be avoided, as data starts to
become overwritten in an implementation depen-
dent way.
The bus master sends from 1 to 32 bytes of data,
each of which is acknowledged by the device if
Write Control (WC) is Low. If Write Control (WC) is
High, the contents of the addressed memory loca-
tion are not modified, and each data byte is fol-
lowed by a NoAck. After each byte is transferred,
the internal byte address counter (the 5 least sig-
nificant address bits only) is incremented. The
transfer is terminated by the bus master generat-
ing a Stop condition.
11/26
M24C64, M24C32
Minimizing System Delays by Polling On ACK

During the internal Write cycle, the device discon-
nects itself from the bus, and writes a copy of the
data from its internal latches to the memory cells.
The maximum Write time (tw) is shown in Table
16. and Table 17., but the typical time is shorter.
To make use of this, a polling sequence can be
used by the bus master.
The sequence, as shown in Figure 9., is: Initial condition: a Write cycle is in progress. Step 1: the bus master issues a Start condition
followed by a Device Select Code (the first
byte of the new instruction). Step 2: if the device is busy with the internal
Write cycle, no Ack will be returned and the
bus master goes back to Step 1. If the device
has terminated the internal Write cycle, it
responds with an Ack, indicating that the
device is ready to receive the second part of
the instruction (the first byte of this instruction
having been sent during Step 1).
M24C64, M24C32
Read Operations

Read operations are performed independently of
the state of the Write Control (WC) signal.
After the successful completion of a Read opera-
tion, the device’s internal address counter is incre-
mented by one, to point to the next byte address.
Random Address Read

A dummy Write is first performed to load the ad-
dress into this address counter (as shown in Fig-
ure 10.) but without sending a Stop condition.
Then, the bus master sends another Start condi-
tion, and repeats the Device Select Code, with the
Read/Write bit (RW) set to 1. The device acknowl-
edges this, and outputs the contents of the ad-
dressed byte. The bus master must not
acknowledge the byte, and terminates the transfer
with a Stop condition.
Current Address Read

For the Current Address Read operation, following
a Start condition, the bus master only sends a De-
vice Select Code with the Read/Write bit (RW) set
to 1. The device acknowledges this, and outputs
the byte addressed by the internal address
counter. The counter is then incremented. The bus
master terminates the transfer with a Stop condi-
tion, as shown in Figure 10., without acknowledg-
ing the byte.
13/26
M24C64, M24C32
Sequential Read

This operation can be used after a Current Ad-
dress Read or a Random Address Read. The bus
master does acknowledge the data byte output,
and sends additional clock pulses so that the de-
vice continues to output the next byte in sequence.
To terminate the stream of bytes, the bus master
must not acknowledge the last byte, and must
generate a Stop condition, as shown in Figure 10..
The output data comes from consecutive address-
es, with the internal address counter automatically
incremented after each byte output. After the last
memory address, the address counter ‘rolls-over’,
and the device continues to output data from
memory address 00h.
Acknowledge in Read Mode

For all Read commands, the device waits, after
each byte read, for an acknowledgment during theth bit time. If the bus master does not drive Serial
Data (SDA) Low during this time, the device termi-
nates the data transfer and switches to its Stand-
by mode.
INITIAL DELIVERY STATE

The device is delivered with all bits in the memory
array set to 1 (each byte contains FFh).
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