CY28RS480

Rev 1.0, November 22, 2006

Page 3 of 14

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. Clock device register changes

are normally made upon system initialization, if any are

required. The interface cannot be used during system

operation for power management functions.

Data Protocol

The clock driver serial protocol accepts byte write, byte 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 (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 individually 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).

Table 1. Command Code Definition

Bit

Description

7

0 = Block read or block write operation, 1 = Byte read or byte write operation

(6:5)

Chip select address, set to ‘00’ to access device

(4:0)

Byte offset for byte read or byte write operation. For block read or block write operations, these bits should be '00000'

Table 2. Block Read and Block Write Protocol

Block Write Protocol

Block Read Protocol

Bit

Description

Bit

Description

1Start

1

Start

8:2

Slave address – 7 bits

8:2

Slave address – 7 bits

9

Write

9

Write

10

Acknowledge from slave

10

Acknowledge from slave

18:11

Command Code – 8 bits

18:11

Command Code – 8 bits

19

Acknowledge from slave

19

Acknowledge from slave

27:20

Byte Count – 8 bits

20

Repeat start

28

Acknowledge from slave

27:21

Slave address – 7 bits

36:29

Data byte 1 – 8 bits

28

Read = 1

37

Acknowledge from slave

29

Acknowledge from slave

45:38

Data byte 2 – 8 bits

37:30

Byte Count from slave – 8 bits

46

Acknowledge from slave

38

Acknowledge

....

Data Byte /Slave Acknowledges

46:39

Data byte 1 from slave – 8 bits

....

Data Byte N – 8 bits

47

Acknowledge

....

Acknowledge from slave

55:48

Data byte 2 from slave – 8 bits

....

Stop

56

Acknowledge

....

Data bytes from slave / Acknowledge

....

Data Byte N from slave – 8 bits

....

NOT Acknowledge

Table 3. Byte Read and Byte Write Protocol

Byte Write Protocol

Byte Read Protocol

Bit

Description

Bit

Description

1Start

1Start

8:2

Slave address – 7 bits

8:2

Slave address – 7 bits

9Write

9Write

10

Acknowledge from slave

10

Acknowledge from slave