ICS841S01 Data Sheet PCI EXPRESSTM CLOCK GENERATOR
ICS841S01CG REVISION B AUGUST 31, 2012 3 ©2012 Integrated Device Technology, Inc.
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 initialize 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 3A.
The block write and block read protocol is outlined in Table 3B, while
Table 3C outlines the corresponding byte write and byte read
protocol. The slave receiver address is 11010010 (D2h).
Table 3A.Command Code Definition
Table 3B. Block Read and Block Write Protocol
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 must be “00000”.
Bit Description = Block Write Bit Description = Block Read
1Start 1Start
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 11:18 Command Code - 8 bits
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 1 - 8 bits 28 Read = 1
37 Acknowledge from slave 29 Acknowledge from slave
38:45 Data byte 2 - 8 bits 30:37 Byte Count from slave - 8 bits
46 Acknowledge from slave 38 Acknowledge
Data Byte/Slave Acknowledges 39:46 Data Byte 1 from slave - 8 bits
Data Byte N - 8 bits 47 Acknowledge
Acknowledge from slave 48:55 Data Byte 2 from slave - 8 bits
Stop 56 Acknowledge
Data Bytes from Slave/Acknowledge
Data Byte N from slave - 8 bits
Not Acknowledge