Si52144

Preliminary Rev. 0.1

11

4. Control Registers

4.1. 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 are individually enabled

or disabled. The registers associated with the Serial Data Interface initialize to their default setting at power-up.

The use of this interface is optional. Clock device register changes are normally made at system initialization, if any

are required. The interface cannot be used during system operation for power management functions.

4.2. 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, access the bytes in sequential order from lowest to highest (most

significant bit first) with the ability to stop after any complete byte is 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 described in Table 1 on page 4.

The block write and block read protocol is outlined in Table 5 while Table 6 outlines byte write and byte read

protocol. The slave receiver address is 11010110 (D6h).

Table 5. Block Read and Block Write Protocol

Block Write Protocol

Block Read Protocol

Bit

Description

Bit

Description

1

Start

1

Start

8:2

Slave address—7 bits

8:2

Slave address—7 bits

9Write

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

....

Stop