24AA32-P MICROCHIP [Microchip Technology], 24AA32-P Datasheet - Page 5

• Manufacturer Part Number: 24AA32-P
• Description: 32K 1.8V I 2 C O Smart Serial EEPROM
• Manufacturer: MICROCHIP [Microchip Technology]

3.6
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 24AA32 this
is set as 1010 binary for read and write operations. The
next three bits of the control byte are the device select
bits (A2, A1, A0). They are used by the master device
to select which of the eight devices are to be accessed.
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 one a
read operation is selected, and when set to a zero a
write operation is selected. The next two bytes received
define the address of the first data byte (Figure 3-3).
Because only A11...A0 are used, the upper four
address bits must be zeros. The most significant bit of
the most significant byte of the address is transferred
first.
Following the start condition, the 24AA32 monitors the
SDA bus checking the device type identifier being
transmitted. Upon receiving a 1010 code and appropri-
ate device select bits, the slave device outputs an
acknowledge signal on the SDA line. Depending on the
state of the R/W bit, the 24AA32 will select a read or
write operation.
FIGURE 3-3:
1996 Microchip Technology Inc.
1
ADDRESS
Device Addressing
SLAVE
0
CONTROL BYTE
1
ADDRESS SEQUENCE BIT ASSIGNMENTS
0
A
2
SELECT
DEVICE
BUS
A
1
This document was created with FrameMaker 4 0 4
A
0 R/W
0
0
ADDRESS BYTE 1
0
0
11
A
FIGURE 3-2:
10
A
Operation
Read
Write
1
A
9
START
A
8
0
Control
SLAVE ADDRESS
Code
1010
1010
1
CONTROL BYTE
ALLOCATION
A
7
ADDRESS BYTE 0
0
Device Address
Device Address
Device Select
A2
READ/WRITE
24AA32
A1
DS21124C-page 5
R/W
A0
A
0
R/W
A
1
0