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24LC04B-ESN Datasheet, PDF (7/34 Pages) Microchip Technology – 4K I2C™ Serial EEPROM | |||
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24AA04/24LC04B
5.0 DEVICE ADDRESSING
A control byte is the first byte received following the
Start condition from the master device. The control byte
consists of a four-bit control code. For the 24XX04, this
is set as â1010â binary for read and write operations.
The next two bits of the control byte are âdonât caresâ for
the 24XX04. The last bit, B0, is used by the master
device to select which of the two 256-word blocks of
memory are to be accessed. This bit is, in effect, the
Most Significant bit of the word address.
The last bit of the control byte defines the operation to
be performed. When set to â1â, a read operation is
selected. When set to â0â, a write operation is selected.
Following the Start condition, the 24XX04 monitors the
SDA bus checking the device type identifier being
transmitted and, upon receiving a â1010â code, the
slave device outputs an Acknowledge signal on the
SDA line. Depending on the state of the R/W bit, the
24XX04 will select a read or write operation.
Operation
Control
Code
Block Select R/W
Read
1010 Block Address 1
Write
1010 Block Address 0
FIGURE 5-1:
CONTROL BYTE
ALLOCATION
Control Code
Read/Write Bit
Block
Select
Bits
S 1 0 1 0 x x B0 R/W ACK
Slave Address
Start Bit
x = âdonât careâ
Acknowledge Bit
FIGURE 5-2:
ADDRESS SEQUENCE BIT ASSIGNMENTS
Control Byte
1
0
1
0
x
x
B
0
R/W
Control
Code
x = âdonât careâ
Block
Select
bits
Address Low Byte
A
7
â¢
â¢
â¢
â¢
â¢
â¢
A
0
© 2009 Microchip Technology Inc.
DS21708K-page 7
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