24AA014H Datasheet, PDF (8/28 Pages) Microchip Technology – 1K I2C™ Serial EEPROM with Half-Array Write-Protect

24AA014H/24LC014H
5.0 DEVICE ADDRESSING
A control byte is the first byte received following the
Start condition from the master device (Figure 5-1).
The control byte consists of a four-bit control code; for
the 24AA014H/24LC014H this is set as ‘1010’ binary
for read and write operations. The next three bits of the
control byte are the Chip Select bits (A2, A1, A0). The
Chip Select bits allow the use of up to eight 24AA014H/
24LC014H devices on the same bus and are used to
select which device is accessed. The Chip Select bits
in the control byte must correspond to the logic levels
on the corresponding A2, A1 and A0 pins for the device
to respond. These bits are in effect the three Most
Significant bits of the word address.
The last bit of the control byte defines the operation to
be performed. When set to a ‘1’, a read operation is
selected. When set to a ‘0’, a write operation is
selected. Following the Start condition, the 24AA014H/
24LC014H monitors the SDA bus, checking the control
byte being transmitted. Upon receiving a ‘1010’ code
and appropriate Chip Select bits, the slave device
outputs an Acknowledge signal on the SDA line.
Depending on the state of the R/W bit, the 24AA014H/
24LC014H will select a read or write operation.
FIGURE 5-1:
CONTROL BYTE FORMAT
Read/Write Bit
Control Code
Chip Select
Bits
S 1 0 1 0 A2 A1 A0 R/W ACK
Start Bit
Slave Address
Acknowledge Bit
5.1 Contiguous Addressing Across
Multiple Devices
The Chip Select bits A2, A1 and A0 can be used to
expand the contiguous address space for up to 8K bits
by adding up to eight 24AA014H/24LC014H devices on
the same bus. In this case, software can use A0 of the
control byte as address bit A8, A1 as address bit A9,
and A2 as address bit A10. It is not possible to
sequentially read across device boundaries.
DS22077B-page 8
Preliminary
© 2008 Microchip Technology Inc.