24VL024H/MNY MICROCHIP [Microchip Technology], 24VL024H/MNY Datasheet - Page 8

• Manufacturer Part Number: 24VL024H/MNY
• Manufacturer: MICROCHIP [Microchip Technology]

24VL024H
5.0
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 24VL024H 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 24VL024H 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 24VL024H
monitors the SDA bus, checking the control byte being
transmitted. Upon receiving a ‘1010’ code and appro-
priate Chip Select bits, the slave device outputs an
Acknowledge signal on the SDA line. Depending on the
state of the R/W bit, the 24VL024H will select a read or
write operation.
DS22109A-page 8
DEVICE ADDRESSING
FIGURE 5-1:
5.1
The Chip Select bits (A2, A1, A0) can be used to
expand the contiguous address space for up to 16K bits
by adding up to eight 24VL024H devices on the same
bus. In this case, software can use A0 of the control
byte as address bit A9, A1 as address bit A10, and A2
as address bit A11. It is not possible to sequentially
read across device boundaries.
Start Bit
S
Contiguous Addressing Across
Multiple Devices
1
Control Code
0
Slave Address
1
CONTROL BYTE FORMAT
© 2008 Microchip Technology Inc.
0
Read/Write Bit
Chip Select
A2
Acknowledge Bit
Bits
A1
A0
R/W
ACK