M34C02(1999) Просмотр технического описания (PDF) - STMicroelectronics
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M34C02 Datasheet PDF : 19 Pages
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M34C02
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.
Power On Reset: VCC Lock-Out Write Protect
In order to prevent data corruption and inadvertent
write operations during power up, a Power On
Reset (POR) circuit is included. The internal reset
is held active until the VCC voltage has reached
the POR threshold value, and all operations are
disabled – the device will not respond to any
command. In the same way, when VCC drops from
the operating voltage, below the POR threshold
value, all operations are disabled and the device
will not respond to any command. A stable and
valid VCC must be applied before applying any
logic signal.
SIGNAL DESCRIPTION
Serial Clock (SCL)
The SCL input pin is used to strobe all data in and
out of the memory. In applications where this line
is used by slaves to synchronize the bus to a
slower clock, the master must have an open drain
output, and a pull-up resistor must be connected
from the SCL line to VCC. (Figure 3 indicates how
the value of the pull-up resistor can be calculated).
In most applications, though, this method of
synchronization is not employed, and so the pull-
up resistor is not necessary, provided that the
master has a push-pull (rather than open drain)
output.
Serial Data (SDA)
The SDA pin is bi-directional, and is used to
transfer data in or out of the memory. 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 the SDA
bus to VCC. (Figure 3 indicates how the value of
the pull-up resistor can be calculated).
Chip Enable (E2, E1, E0)
These chip enable inputs 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 may be driven dynamically or tied to
VCC or VSS to establish the device select code.
Write Control (WC)
A hardware Write Control (WC, pin 7) is provided
for protecting the contents of the whole memory
from erroneous erase/write cycles. The Write
Control signal is used to enable (WC=VIL) or
disable (WC=VIH) write instructions to the entire
memory area or to the Protection Register.
When WC is tied to VSS or left unconnected, the
write protection of the first half of the memory is
determined by the status of the Protection
Register.
DEVICE OPERATION
The memory 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 master, and the other as
the slave. A data transfer can only be initiated by
the master, which will also provide the serial clock
for synchronization. The memory device is always
a slave device in all communication.
Figure 3. Maximum RL Value versus Bus Capacitance (CBUS) for an I2C Bus
VCC
20
16
12
8
4
0
10
fc = 100kHz
fc = 400kHz
100
CBUS (pF)
RL
SDA
MASTER
SCL
RL
CBUS
1000
CBUS
AI01665
3/19
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