64 Kbit EEPROM with password protection & dual interface:
SO8 (MN)
150 mils width
UFDFPN8 (MB)
2 × 3 mm
TSSOP8 (DW)
Sawn wafer on UV tape
400 kHz I²C serial bus & ISO 15693 RF protocol at 13.56 MHz
Features
I2C interface
■ Two-wire I
protocol
■ Single supply voltage:
– 1.8 V to 5.5 V
■ Byte and Page Write (up to 4 bytes)
■ Random and Sequential Read modes
■ Self-timed programming cycle
■ Automatic address incrementing
■ Enhanced ESD/latch-up protection
Contactless interface
2
C serial interface supports 400 kHz
M24LR64-R
■ ISO 15693 and ISO 18000-3 mode 1
compatible
■ 13.56 MHz ±7k Hz carrier frequency
■ To tag: 10% or 100% ASK modulation using
1/4 (26 Kbit/s) or 1/256 (1.6 Kbit/s) pulse
position coding
■ From tag: load modulation using Manchester
coding with 423 kHz and 484 kHz subcarriers
in low (6.6 kbit/s) or high (26 kbit/s) data rate
mode. Supports the 53 kbit/s data rate with
Fast commands
■ Internal tuning capacitance: 27.5 pF
■ 64-bit unique identifier (UID)
■ Read Block & Write (32-bit Blocks)
Memory
■ 64 Kbit EEPROM organized into:
– 8192 bytes in I
– 2048 blocks of 32 bits in RF mode
The M24LR64-R device is a dual-interface, electrically erasable programmable memory
(EEPROM). It features an I
also a contactless memory powered by the received carrier electromagnetic wave. The
M24LR64-R is organized as 8192 × 8 bits in the I
2
C interface and can be operated from a VCC power supply. It is
2
C mode and as 2048 × 32 bits in the ISO
15693 and ISO 18000-3 mode 1 RF mode.
Figure 1.Logic diagram
2
I
C uses a two-wire serial interface, comprising a bidirectional data line and a clock line. The
devices carry a built-in 4-bit device type identifier code (1010) in accordance with the I
2
C
bus definition.
The device behaves as a slave in the I
2
C protocol, with all memory operations synchronized
by the serial clock. Read and Write operations are initiated by a Start condition, generated
by the bus master. The Start condition is followed by a device select code and Read/Write
bit (RW
) (as described in Ta bl e 2 ), terminated by an acknowledge bit.
When writing data to the memory, the device inserts an acknowledge bit during the 9
th
bit
time, following the bus master’s 8-bit transmission. When data is read by the bus master, the
bus master acknowledges the receipt of the data byte in the same way. Data transfers are
terminated by a Stop condition after an Ack for Write, and after a NoAck for Read.
In the ISO15693/ISO18000-3 mode 1 RF mode, the M24LR64-R is accessed via the
13.56 MHz carrier electromagnetic wave on which incoming data are demodulated from the
received signal amplitude modulation (ASK: amplitude shift keying). The received ASK wave
is 10% or 100% modulated with a data rate of 1.6 Kbit/s using the 1/256 pulse coding mode
or a data rate of 26 Kbit/s using the 1/4 pulse coding mode.
Outgoing data are generated by the M24LR64-R load variation using Manchester coding
with one or two subcarrier frequencies at 423 kHz and 484 kHz. Data are transferred from
the M24LR64-R at 6.6 Kbit/s in low data rate mode and 26 Kbit/s high data rate mode. The
M24LR64-R supports the 53 Kbit/s in high data rate mode in one subcarrier frequency at
423 kHz.
The M24LR64-R follows the ISO 15693 and ISO 18000-3 mode 1 recommendation for
radio-frequency power and signal interface.
12/128Doc ID 15170 Rev 14
M24LR64-RDescription
SDAV
SS
SCL
E1AC0
E0V
CC
AC1
AI15107
1
2
3
4
8
7
6
5
Table 1.Signal names
Signal nameFunctionDirection
E0, E1Chip EnableInput
SDASerial DataI/O
SCLSerial ClockInput
AC0, AC1Antenna coilsI/O
V
CC
V
SS
Supply voltage
Ground
Figure 2.8-pin package connections
1. See Package mechanical data section for package dimensions, and how to identify pin-1.
Doc ID 15170 Rev 1413/128
Signal descriptionM24LR64-R
Ai12806
V
CC
M24xxx
V
SS
E
i
V
CC
M24xxx
V
SS
E
i
2 Signal description
2.1 Serial Clock (SCL)
This input signal is used to strobe all data in and out of the device. In applications 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 V
most applications, though, this method of synchronization is not employed, and so the pullup resistor is not necessary, provided that the bus master has a push-pull (rather than open
drain) output.
2.2 Serial Data (SDA)
This bidirectional 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 Serial Data (SDA) to V
the value of the pull-up resistor can be calculated).
. (Figure 4 indicates how the value of the pull-up resistor can be calculated). In
CC
. (Figure 4 indicates how
CC
2.3 Chip Enable (E0, E1)
These input signals are used to set the value that is to be looked for on the two least
significant bits (b2, b1) of the 7-bit device select code. These inputs must be tied to V
V
, to establish the device select code as shown in Figure 3. When not connected (left
SS
floating), these inputs are read as low (0,0).
Figure 3.Device select code
2.4 Antenna coil (AC0, AC1)
These inputs are used to connect the device to an external coil exclusively. It is advised to
not connect any other DC or AC path to AC0 and AC1 pads. When correctly tuned, the coil
is used to power and access the device using the ISO 15693 and ISO 18000-3 mode 1
protocols.
CC
or
14/128Doc ID 15170 Rev 14
M24LR64-RSignal description
2.5 VSS ground
VSS is the reference for the VCC supply voltage.
2.6 Supply voltage (VCC)
This pin can be connected to an external DC supply voltage.
Note:An internal voltage regulator allows the external voltage applied on V
M24LR64-R, while preventing the internal power supply (rectified RF waveforms) to output a
DC voltage on the V
2.6.1 Operating supply voltage V
CC
pin.
CC
Prior to selecting the memory and issuing instructions to it, a valid and stable VCC voltage
within the specified [V
(min), VCC(max)] range must be applied (see Tab l e 1 00 ). To
CC
maintain a stable DC supply voltage, it is recommended to decouple the V
suitable capacitor (usually of the order of 10 nF) close to the V
CC/VSS
This voltage must remain stable and valid until the end of the transmission of the instruction
and, for a Write instruction, until the completion of the internal I²C write cycle (t
2.6.2 Power-up conditions
When the power supply is turned on, VCC rises from VSS to VCC. The VCC rise time must not
vary faster than 1V/µs.
2.6.3 Device reset
In order to prevent inadvertent write operations during power-up, a power-on reset (POR)
circuit is included. At power-up (continuous rise of V
instruction until V
lower than the minimum V
has reached the power-on reset threshold voltage (this threshold is
CC
operating voltage defined in Ta bl e 1 00 ). When VCC passes
CC
over the POR threshold, the device is reset and enters the Standby Power mode, however,
the device must not be accessed until V
within the specified [V
(min), VCC(max)] range.
CC
has reached a valid and stable VCC voltage
CC
In a similar way, during power-down (continuous decrease in V
below the power-on reset threshold voltage, the device stops responding to any instruction
sent to it.
), the device does not respond to any
CC
), as soon as VCC drops
CC
to supply the
CC
line with a
CC
package pins.
).
W
2.6.4 Power-down conditions
During power-down (continuous decay of VCC), the device must be in Standby Power mode
(mode reached after decoding a Stop condition, assuming that there is no internal write
cycle in progress).
Doc ID 15170 Rev 1415/128
Signal descriptionM24LR64-R
1
10
100
101001000
Bus line capacitor (pF)
Bus line pull-up resistor
(k
)
When t
LOW
= 1.3 µs (min value for
f
C
= 400 kHz), the R
bus
× C
bus
time constant m ust be below the
400 ns time constant line
represented on the left.
I²C bus
master
M24xxx
R
bus
V
CC
C
bus
SCL
SDA
ai14796b
R
bus
× C
bus
= 400 ns
Here R
bus
× C
bus
= 120 ns
4 kΩ
30 pF
SCL
SDA
SCL
SDA
SDA
Start
Condition
SDA
Input
SDA
Change
AI00792B
Stop
Condition
123789
MSB
ACK
Start
Condition
SCL
123789
MSBACK
Stop
Condition
Figure 4.I2C Fast mode (fC = 400 kHz): maximum R
Figure 5.I
capacitance (C
2
C bus protocol
bus
)
value versus bus parasitic
bus
16/128Doc ID 15170 Rev 14
M24LR64-RSignal description
Table 2.Device select code
Device type identifier
(1)
Chip Enable address
b7b6b5b4b3b2b1b0
Device select code1010E2
1. The most significant bit, b7, is sent first.
2. E0 and E1 are compared against the respective external pins on the memory device.
3. E2 is not connected to any external pin. It is however used to address the M24LR64-R as described in
Section 3 and Section 4.
Table 3.Address most significant byte
(3)
E1E0RW
b15 b14 b13 b12 b11 b10 b9 b8
Table 4.Address least significant byte
b7 b6 b5 b4 b3 b2 b1 b0
(2)
RW
Doc ID 15170 Rev 1417/128
User memory organizationM24LR64-R
3 User memory organization
The M24LR64-R is divided into 64 sectors of 32 blocks of 32 bits as shown in Tab l e 5 .
Figure 7 shows the memory sector organization. Each sector can be individually read-
and/or write-protected using a specific password command. Read and write operations are
possible if the addressed data are not in a protected sector.
The M24LR64-R also has a 64-bit block that is used to store the 64-bit unique identifier
(UID). The UID is compliant with the ISO 15963 description, and its value is used during the
anticollision sequence (Inventory). This block is not accessible by the user and its value is
written by ST on the production line.
The M24LR64-R includes an AFI register that stores the application family identifier, and a
DSFID register that stores the data storage family identifier used in the anticollision
algorithm.
The M24LR64-R has four additional 32-bit blocks that store an I
password codes.
Figure 6.Block diagram
2
C password plus three RF
AC0
AC1
RF
RF V
CC
EEPROM
Row decoder
Latch
Logic
Power management
I2C
Contact V
CC
SCL
SDA
V
CC
V
SS
ai15123
18/128Doc ID 15170 Rev 14
M24LR64-RUser memory organization
0 1 Kbit EEPROM sector 5 bits
1 1 Kbit EEPROM sector 5 bits
2 1 Kbit EEPROM sector 5 bits
3 1 Kbit EEPROM sector 5 bits
60 1 Kbit EEPROM sector 5 bits
61 1 Kbit EEPROM sector 5 bits
62 1 Kbit EEPROM sector 5 bits
63 1 Kbit EEPROM sector 5 bits
I2C Password System
RF Password 1 System
RF Password 2 System
RF Password 3 System
8 bit DSFID System
8 bit AFI System
64 bit UID System
Sector Area Sector security
status
ai15124
Figure 7.Memory sector organization
Sector details
The M24LR64-R user memory is divided into 64 sectors. Each sector contains 1024 bits.
The protection scheme is described in Section 4: System memory area.
In RF mode, a sector provides 32 blocks of 32 bits. Each read and write access are done by
block. Read and write block accesses are controlled by a Sector Security Status byte that
defines the access rights to all the 32 blocks contained in the sector. If the sector is not
protected, a Write command updates the complete 32 bits of the selected block.
2
In I
C mode, a sector provides 128 bytes that can be individually accessed in read and write
modes. When protected by the corresponding I2C_Write_Lock bit, the entire sector is writeprotected. To access the user memory, the device select code used for any I
must have the E2 Chip Enable address at 0.
2
C command
Doc ID 15170 Rev 1419/128
User memory organizationM24LR64-R
Table 5.Sector details
Sector
number
0
RF block
address
I2C byte
address
Bits [31:24]Bits [23:16]Bits [15:8]Bits [7:0]
00useruseruseruser
14useruseruseruser
28useruseruseruser
312useruseruseruser
416useruseruseruser
520useruseruseruser
624useruseruseruser
728useruseruseruser
832useruseruseruser
936useruseruseruser
1040useruseruseruser
1144useruseruseruser
1248useruseruseruser
1352useruseruseruser
1456useruseruseruser
1560useruseruseruser
1664useruseruseruser
1768useruseruseruser
1872useruseruseruser
1976useruseruseruser
2080useruseruseruser
2184useruseruseruser
2288useruseruseruser
2392useruseruseruser
2496useruseruseruser
25100useruseruseruser
26104useruseruseruser
27108useruseruseruser
28112useruseruseruser
29116useruseruseruser
30120useruseruseruser
31124useruseruseruser
20/128Doc ID 15170 Rev 14
M24LR64-RUser memory organization
Table 5.Sector details (continued)
Sector
number
1
.....................
RF block
address
32128useruseruseruser
33132useruseruseruser
34136useruseruseruser
35140useruseruseruser
36144useruseruseruser
37148useruseruseruser
38152useruseruseruser
39156useruseruseruser
..................
I2C byte
address
Bits [31:24]Bits [23:16]Bits [15:8]Bits [7:0]
Doc ID 15170 Rev 1421/128
User memory organizationM24LR64-R
Table 5.Sector details (continued)
Sector
number
63
RF block
address
20168064useruseruseruser
20178068useruseruseruser
20188072useruseruseruser
20198076useruseruseruser
20208080useruseruseruser
20218084useruseruseruser
20228088useruseruseruser
20238092useruseruseruser
20248096useruseruseruser
20258100useruseruseruser
20268104useruseruseruser
20278108useruseruseruser
20288112useruseruseruser
20298116useruseruseruser
20308120useruseruseruser
20318124useruseruseruser
20328128useruseruseruser
I2C byte
address
Bits [31:24]Bits [23:16]Bits [15:8]Bits [7:0]
20338132useruseruseruser
20348136useruseruseruser
20358140useruseruseruser
20368144useruseruseruser
20378148useruseruseruser
20388152useruseruseruser
20398156useruseruseruser
20408160useruseruseruser
20418164useruseruseruser
20428168useruseruseruser
20438172useruseruseruser
20448176useruseruseruser
20458180useruseruseruser
20468184useruseruseruser
20478188useruseruseruser
22/128Doc ID 15170 Rev 14
M24LR64-RSystem memory area
4 System memory area
4.1 M24LR64-R RF block security
The M24LR64-R provides a special protection mechanism based on passwords. Each
memory sector of the M24LR64-R can be individually protected by one out of three available
passwords, and each sector can also have Read/Write access conditions set.
Each memory sector of the M24LR64-R is assigned with a Sector security status byte
including a Sector Lock bit, two Password Control bits and two Read/Write protection bits as
shown in Ta bl e 7 . Tab le 6 describes the organization of the Sector security status byte which
can be read using the Read Single Block and Read Multiple Block commands with the
Option_flag set to ‘1’.
On delivery, the default value of the SSS bytes is reset to 00h.
When the Sector Lock bit is set to ‘1’, for instance by issuing a Lock-sector Password
command, the 2 Read/Write protection bits (b
, b2) are used to set the Read/Write access of
1
the sector as described in Ta b l e 8 .
Doc ID 15170 Rev 1423/128
System memory areaM24LR64-R
Table 8.Read / Write protection bit setting
Sector
Lock
b
2
Sector access when password
, b
1
presented
Sector access when password not
presented
0xxReadWriteReadWrite
100ReadWriteReadNo Write
101ReadWriteReadWrite
110ReadWriteNo ReadNo Write
111ReadNo WriteNo ReadNo Write
The next 2 bits of the Sector security status byte (b3, b4) are the Password Control bits. The
value these two bits is used to link a password to the sector as defined in Ta b le 9 .
Table 9.Password Control bits
b4, b
3
Password
00The sector is not protected by a Password
01The sector is protected by the Password 1
10The sector is protected by the Password 2
11The sector is protected by the Password 3
The M24LR64-R password protection is organized around a dedicated set of commands
plus a system area of three password blocks where the password values are stored. This
system area is described in Ta bl e 1 0.
Table 10.Password system area
Block number32-bit password number
1Password 1
2Password 2
3Password 3
The dedicated password commands are:
●Write-sector Password:
The Write-sector Password command is used to write a 32-bit block into the password
system area. This command must be used to update password values. After the write
cycle, the new password value is automatically activated. It is possible to modify a
password value after issuing a valid Present-sector Password command.
On delivery, the three default password values are set to 0000 0000h and are activated.
●Lock-sector Password:
The Lock-sector Password command is used to set the Sector security status byte of
the selected sector. Bits b
to b1 of the Sector security status byte are affected by the
4
Lock-sector Password command. The Sector Lock bit, b
After issuing a Lock-sector Password command, the protection settings of the selected
sector are activated. The protection of a locked block cannot be changed in RF mode.
A Lock-sector Password command sent to a locked sector returns an error code.
24/128Doc ID 15170 Rev 14
, is set to ‘1’ automatically.
0
M24LR64-RSystem memory area
●Present-sector Password:
The Present-sector Password command is used to present one of the three passwords
to the M24LR64-R in order to modify the access rights of all the memory sectors linked
to that password (Ta bl e 8 ) including the password itself. If the presented password is
correct, the access rights remain activated until the tag is powered off or until a new
Present-sector Password command is issued. If the presented password value is not
correct, all the access rights of all the memory sectors are deactivated.
●Sector security status byte area access conditions in I
2
In I
C mode, read access to the Sector security status byte area is always allowed.
Write access depends on the correct presentation of the I
2
C mode:
2
C password (see I2C
Present Password command description on page 27).
To access the Sector security status byte area, the device select code used for any I
2
C
command must have the E2 Chip Enable address at 1.
2
An I
C write access to a Sector security status byte re-initializes the RF access
condition to the given memory sector.
4.2 Example of the M24LR64-R security protection
Ta bl e 1 1 and Ta bl e 1 2 show the sector security protections before and after a valid Present-
sector Password command. Tab le 1 1 shows the sector access rights of an M24LR64-R after
power-up. After a valid Present-sector Password command with password 1, the memory
sector access is changed as shown in Ta b le 12 .
Table 11.M24LR64-R sector security protection after power-up
Sector
address
0 Protection: Standard ReadNo Writexxx 00001
1 Protection: Pswd 1ReadNo Writexxx 01001
2 Protection: Pswd 1ReadWritexxx 01011
3 Protection: Pswd 1No ReadNo Writexxx 01101
4 Protection: Pswd 1No ReadNo Writexxx 01111
Table 12.M24LR64-R sector security protection after a valid presentation of
Sector security status byte
b
7b6b5b4b3b2b1b0
password 1
Sector
address
0Protection: StandardReadNo Writexxx00001
1Protection: Pswd 1ReadWritexxx01001
2Protection: Pswd 1ReadWritexxx01011
3Protection: Pswd 1ReadWritexxx01101
4Protection: Pswd 1ReadNo Writexxx01111
Sector security status byte
b7b6b5b4b3b2b1b
0
Doc ID 15170 Rev 1425/128
System memory areaM24LR64-R
4.3 I2C_Write_Lock bit area
In the I2C mode only, it is possible to protect individual sectors against Write operations.
This feature is controlled by the I2C_Write_Lock bits stored in the 8 bytes of the
I2C_Write_Lock bit area starting from the location 2048 (see Ta bl e 1 3 ). Using these 64 bits,
it is possible to write-protect all the 64 sectors of the M24LR64-R memory.
Each bit controls the I
possible to unprotect a sector in the I
the corresponding sector is unprotected. When the bit is set to 1, the corresponding sector
is write-protected.
2
In I
C mode, read access to the I2C_Write_Lock bit area is always allowed. Write access
depends on the correct presentation of the I
To access the I2C_Write_Lock bit area, the device select code used for any I
must have the E2 Chip Enable address at 1.
On delivery, the default value of the 8 bytes of the I2C_Write_Lock bit area is reset to 00h.
C write access to a specific sector as shown in Ta b le 13 . It is always
2
C mode. When an I2C_Write_Lock bit is reset to 0,
2
C password.
2
C command
4.4 System parameters
The M24LR64-R provides the system area required by the ISO 15693 RF protocol, as
shown in Ta bl e 1 4 .
The first 32-bit block starting from I
is used to activate/deactivate the write protection of the protected sector in I
power-on, all user memory sectors protected by the I2C_Write_Lock bits can be read but
cannot be modified. To remove the write protection, it is necessary to use the I
Password described in Figure 8. When the password is correctly presented — that is, when
all the presented bits correspond to the stored ones — it is also possible to modify the I
password using the I
The next three 32-bit blocks store the three RF passwords. These passwords are neither
read- nor write- accessible in the I
The next 2 bytes are used to store the AFI, at I
location 2323. These 2 values are used during the RF Inventory sequence. They are readonly in the I
2
C mode.
The next 8 bytes, starting from location 2324, store the 64-bit UID programmed by ST on the
production line. Bytes at I
used by the RF Get_System_Info command. The UID, Mem_Size and IC Ref values are
read-only data.
2
C Write Password command described in Figure 9.
2
C locations 2332 to 2335 store the IC Ref and the Mem_Size data
2
C address 2304 stores the I2C password. This password
The M24LR64-R controls I2C sector write access using the 32-bit-long I2C password and
the 64-bit I2C_Write_Lock bit area. The I
commands: I
2
C Present Password and I2C Write Password.
2
C password value is managed using two I2C
4.5.1 I2C Present Password command description
The I2C Present Password command is used in I2C mode to present the password to the
M24LR64-R in order to modify the write access rights of all the memory sectors protected by
the I2C_Write_Lock bits, including the password itself. If the presented password is correct,
the access rights remain activated until the M24LR64-R is powered off or until a new I
Present Password command is issued.
Following a Start condition, the bus master sends a device select code with the Read/Write
bit (RW
in Figure 8, and waits for two I
responds to each address byte with an acknowledge bit, and then waits for the 4 password
data bytes, the validation code, 09h, and a resend of the 4 password data bytes. The most
significant byte of the password is sent first, followed by the least significant bytes.
It is necessary to send the 32-bit password twice to prevent any data corruption during the
sequence. If the two 32-bit passwords sent are not exactly the same, the M24LR64-R does
not start the internal comparison.
When the bus master generates a Stop condition immediately after the Ack bit (during the
“10
condition at any other time does not trigger the internal delay. During that delay, the
M24LR64-R compares the 32 received data bits with the 32 bits of the stored I
If the values match, the write access rights to all protected sectors are modified after the
internal delay. If the values do not match, the protected sectors remains protected.
) reset to 0 and the Chip Enable bit E2 at 1. The device acknowledges this, as shown
th
bit” time slot), an internal delay equivalent to the write cycle time is triggered. A Stop
2
C password address bytes 09h and 00h. The device
2
C
2
C password.
During the internal delay, Serial Data (SDA) is disabled internally, and the device does not
respond to any requests.
Doc ID 15170 Rev 1427/128
System memory areaM24LR64-R
ai15125b
Start
Device select
code
Password
address 09h
Password
address 00h
Password
[31:24]
Ack
R/W
AckAckAck
Device select code = 1010 1 E1 E0
Password
[23:16]
Password
[15:8]
Password
[7:0]
AckAckAck
Ack generated during
9
th
bit time slot.
Stop
Validation
code 09h
Ack
Password
[31:24]
Ack
Password
[23:16]
Password
[15:8]
Password
[7:0]
AckAckAck
Figure 8.I2C Present Password command
4.5.2 I2C Write Password command description
The I2C Write Password command is used to write a 32-bit block into the M24LR64-R I2C
password system area. This command is used in I
value. It cannot be used to update any of the RF passwords. After the write cycle, the new
2
I
C password value is automatically activated. The I2C password value can only be modified
after issuing a valid I
On delivery, the I
2
C Present Password command.
2
C default password value is set to 0000 0000h and is activated.
2
C mode to update the I2C password
Following a Start condition, the bus master sends a device select code with the Read/Write
bit (RW
in Figure 9, and waits for the two I
) reset to 0 and the Chip Enable bit E2 at 1. The device acknowledges this, as shown
2
C password address bytes, 09h and 00h. The device
responds to each address byte with an acknowledge bit, and then waits for the 4 password
data bytes, the validation code, 07h, and a resend of the 4 password data bytes. The most
significant byte of the password is sent first, followed by the least significant bytes.
It is necessary to send twice the 32-bit password to prevent any data corruption during the
write sequence. If the two 32-bit passwords sent are not exactly the same, the M24LR64-R
does not modify the I
When the bus master generates a Stop condition immediately after the Ack bit (during the
th
10
bit time slot), the internal write cycle is triggered. A Stop condition at any other time
2
C password value.
does not trigger the internal write cycle.
During the internal write cycle, Serial Data (SDA) is disabled internally, and the device does
not respond to any requests.
The device supports the I2C protocol. This is summarized 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 device. A data transfer can only be initiated by the bus master, which will
also provide the serial clock for synchronization. The M24LR64-R device is always a slave in
all communications.
5.1 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.
5.2 Stop condition
Stop is identified by a rising edge of Serial Data (SDA) while Serial Clock (SCL) is stable
and driven high. A Stop condition terminates communication 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 Standby mode. A Stop condition at the end of a Write command
triggers the internal write cycle.
5.3 Acknowledge bit (ACK)
The acknowledge bit is used to indicate a successful byte transfer. The bus transmitter,
whether it be bus master or slave device, releases Serial Data (SDA) after sending eight bits
of data. During the 9
acknowledge the receipt of the eight data bits.
th
clock pulse period, the receiver pulls Serial Data (SDA) low to
5.4 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 driven low.
30/128Doc ID 15170 Rev 14
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