CY28312B-2

Rev 1.0, November 21, 2006

Page 3 of 17

Serial Data Interface

The CY28312B-2 features a two-pin, serial data interface that

can be used to configure internal register settings that control

particular device functions.

Data Protocol

The clock driver serial protocol supports byte/word write,

byte/word read, block write and block read operations from the

controller. For block write/read operation, the bytes must be

accessed in sequential order from lowest to highest byte with

the ability to stop after any complete byte has been trans-

ferred. For byte/word write and byte read operations, system

controller can access individual indexed byte. The offset of the

indexed byte is encoded in the command code.

The definition for the command code is defined in Table 1.

SDATA

31

I/O

Data pin for SMBus circuitry.

SCLK

30

I

Clock pin for SMBus circuitry.

VDD_CPU

40

P

2.5V Power Connection. Power supply for CPU output buffers. Connect to

2.5V.

VDDQ_AGP

25

P

3.3V Power Connection. Power supply for AGP output buffers. Connect to 3.3V.

VDDQ_PCI

15, 23

P

3.3V Power Connection. Power supply for PCI output buffers. Connect to 3.3V.

VDDQ_48MHz

5

P

3.3V Power Connection. Power supply for 48-MHz output buffers. Connect to 3.3V.

VDD_REF

1

P

3.3V Power Connection: Power supply for reference output buffers. Connect

to 3.3V.

VDD_Core

33

P

3.3V Power Connection: Power supply for PLL core. Connect to 3.3V.

GND_REF,

GND_48MHz,

GND_PCI,

GND_AGP,

GND_Core,

GND_CPU

2, 8, 29, 32, 37,

43

G

Ground Connections: Connect all ground pins to the common system ground

plane.

Pin Name

Pin No.

Pin

Type

Pin Description

Bit

Descriptions

7

0 = Block read or block write operation

1 = Byte/Word read or byte/word write operation

6:0

Byte offset for byte/word read or write operation. For block read or write operations, these bits

need to be set at ‘0000000’.

Table 1. Block Read and Block Write Protocol

Block Write Protocol

Block Read Protocol

Bit

Description

Bit

Description

1

Start

1

Start

2:8

Slave address – 7 bits

2:8

Slave address – 7 bits

9Write

9Write

10

Acknowledge from slave

10

Acknowledge from slave

11:18

Command Code – 8 bits

‘00000000’ stands for block operation

11:18

Command Code – 8 bits

‘00000000’ stands for block operation

19

Acknowledge from slave

19

Acknowledge from slave

20:27

Byte Count – 8 bits

20

Repeat start

28

Acknowledge from slave

21:27

Slave address – 7 bits

29:36

Data byte 0 – 8 bits

28

Read

37

Acknowledge from slave

29

Acknowledge from slave

38:45

Data byte 1 – 8 bits

30:37

Byte count from slave – 8 bits

46

Acknowledge from slave

38

Acknowledge