Si53154
10 Rev. 1.3
4. Control Registers
4.1. I
2
C Interface
To enhance the flexibility and function of the clock buffer, an I
2
C interface is provided. Through the I
2
C Interface,
various device functions are available, such as individual clock output enable. The registers associated with the I
2
C
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. Power management functions can only be
programed in program mode and not in normal operation modes.
4.2. Data Protocol
The I
2
C 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 block write and block read protocol is outlined in Table 4 while Table 5 outlines byte write and byte read
protocol. The slave receiver address is 11010110 (D6h).
Table 4. 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 9Write
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
