Datasheet

24AA01/24LC01B
DS21711C-page 6  2003 Microchip Technology Inc.
3.6 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 24XX01, this
is set as ‘
1010’ binary for read and write operations.
The next three bits of the control byte are ‘don’t care’s’
for the 24XX01.
The last bit of the control byte defines the operation to
be performed. When set to ‘
1’, a read operation is
selected. When set to ‘
0’, a write operation is selected.
Following the Start condition, the 24XX01 monitors the
SDA bus checking the device type identifier being
transmitted. Upon receiving a ‘
1010’ code, the slave
device outputs an Acknowledge signal on the SDA line.
Depending on the state of the R/W bit, the 24XX01 will
select a read or write operation.
FIGURE 3-2: CONTROL BYTE
ALLOCATION
Operation
Control
Code
Block Select R/W
Read 1010 Block Address 1
Write 1010 Block Address 0
1010XXX
R/W
A
START READ/WRITE
SLAVE ADDRESS
X = ‘Don’t care’.