M34C00 查看數據表（PDF） - STMicroelectronics
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M34C00 Datasheet PDF : 15 Pages
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Figure 3. Maximum RL Value versus Bus Capacitance (CBUS) for an I2C Bus
VCC
20
M34C00
16
12
8
4
0
10
fc = 100kHz
fc = 400kHz
100
CBUS (pF)
RL
SDA
MASTER
SCL
RL
CBUS
1000
CBUS
AI01665
collector signals on the bus. A pull up resistor must
be connected from Serial Data (SDA) to VCC.
(Figure 3 indicates how the value of the pull-up
resistor can be calculated).
DEVICE OPERATION
The device supports the I2C protocol. This is
summarized in Figure 4. 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 M34C00
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 programming 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
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 Stand-by mode. A Stop
condition at the end of a Write command triggers
the internal EEPROM Write cycle.
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 9th 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 data on Serial Data (SDA)
Table 3. Device Select Code
Device Type Identifier1
RW
b7
b6
b5
b4
b3
b2
b1
b0
Memory Area Select Code (three arrays) 1
0
1
0
1
1
1
RW
Protection Register Select Code
0
1
1
0
1
1
1
RW
Note: 1. The most significant bit (b7) is sent first.
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