M24C16, M24C08, M24C04, M24C02, M24C01
DEVICE OPERATION
The device supports the I²C protocol. This is sum-
marized in Figure 6.. 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.
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.
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.
Each device is given a unique 3-bit code on the
Chip Enable (E0, E1, E2) inputs. When the Device
Select Code is received, the device only responds
if the Chip Enable Address is the same as the val-
ue on the Chip Enable (E0, E1, E2) inputs. How-
ever, those devices with larger memory capacities
(the M24C16, M24C08 and M24C04) need more
address bits. E0 is not available for use on devices
that need to use address line A8; E1 is not avail-
able for devices that need to use address line A9,
and E2 is not available for devices that need to use
address line A10 (see Figure 3. and Table 3. for
details). Using the E0, E1 and E2 inputs, up to
eight M24C02 (or M24C01), four M24C04, two
M24C08 or one M24C16 devices can be connect-
ed to one I²C bus. In each case, and in the hybrid
cases, this gives a total memory capacity of
16 Kbits, 2 KBytes (except where M24C01 devic-
es are used).
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
th
The 8 bit is the Read/Write bit (RW). This bit is
(SDA) after sending eight bits of data. During the
th
set to 1 for Read and 0 for Write operations.
9
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
If a match occurs on the Device Select code, the
corresponding device gives an acknowledgment
on Serial Data (SDA) during the 9 bit time. If the
device does not match the Device Select code, it
deselects itself from the bus, and goes into Stand-
by mode.
th
Table 4. Operating Modes
1
Mode
RW bit
Bytes
Initial Sequence
WC
X
Current Address Read
1
0
1
1
0
0
1
START, Device Select, RW = 1
X
START, Device Select, RW = 0, Address
reSTART, Device Select, RW = 1
Similar to Current or Random Address Read
START, Device Select, RW = 0
Random Address Read
1
X
Sequential Read
Byte Write
X
≥ 1
1
VIL
VIL
Page Write
≤16
START, Device Select, RW = 0
Note: 1. X = VIH or VIL.
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STMICROELECTRONICS [ ST ]
