24AA01/24LC01B
3.6
Device Addressing
FIGURE 3-2:
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 cares”
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.
Operation
Read
Write
Control
Code
1010
1010
Block Select
Block Address
Block Address
R/W
1
0
S
1
CONTROL BYTE
ALLOCATION
Read/Write Bit
Block
Select
Bits
x
x
x
R/W ACK
Control Code
0
1
0
Slave Address
Start Bit
x = “don’t care”
Acknowledge Bit
DS21711G-page 6
©
2007 Microchip Technology Inc.
MICROCHIP [ MICROCHIP TECHNOLOGY ]
