CY28359

Rev 1.0, November 24, 2006

Page 2 of 7

Serial Data Interface

To enhance the flexibility and function of the clock synthesizer,

a two-signal serial interface is provided. Through the Serial

Data Interface, various device functions, such as individual

clock output buffers, can be individually enabled or disabled.

The registers associated with the Serial Data Interface

initializes to their default setting upon power-up, and therefore

use of this interface is optional. The interface can also be

accessed during power down operation.

Data Protocol

The clock driver serial protocol accepts Byte Write, Byte Read,

controller. For Block Write/Read operation, the bytes must be

accessed in sequential order from lowest to highest byte (most

significant bit first) with the ability to stop after any complete

byte has been transferred. For Byte Write and Byte Read

operations, the system controller can access individual

indexed bytes. The offset of the indexed byte is encoded in the

command code, as described in Table 1.

The Block Write and Block Read protocol is outlined in Table 2

while Table 3 outlines the corresponding Byte Write and Byte

Read protocol.The slave receiver address is 11010010 (D2h)

or 11011100 (DCh) depending on state of ADDRSEL.

Pin Description

Pin

Name

PWR

I/O

Description

10

2

BUF_INA,

BUF_INB

VDD2.5

I

Reference input from chipset. 2.5V input.

13,15,20

4,6,24

DDRA[0:2]C

DDRB[0:2]C

VDD2.5

O

Clock outputs. These outputs provide complementary

copies of BUF_INA & BUF_INB, respectively.

12,14,21

3,5,25

DDRA[0:2]T

DDRB[0:2]T

VDD2.5

O

Clock outputs. These outputs provide copies of BUF_INA

& BUF_INB, respectively.

9

1

FB_OUTA

FB_OUTB

VDD2.5

O

Feedback clock for chipset

18

SCLK

VDD2.5

I

SMBus clock input. Has pull-up resistor

19

SDATA

VDD2.5

I/O

SMBus data input. Has pull-up resistor

26

SEL_ADDR

I

Address Select Pin. Has pull-down resistor

7,16,22,28

VDD2.5

2.5V voltage supply

8,11,17,23,27

VSS

Ground

Table 1. Command Code Definition

Bit

Description

7

0 = Block Read or Block Write operation

1 = Byte Read or Byte Write operation

(6:5)

01

(4:0)

Byte offset for Byte Read or Byte Write operation. For Block Read or Block Write operations, these bits should be '00000'