CY28325-3
Serial Data Interface
Data Protocol
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 initial-
izes 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 pow-
er management functions.
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 se-
quential 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 sys-
tem controller can access individually indexed bytes. The off-
set of the indexed byte is encoded in the command code, as
described in Table 2.
The block write and block read protocol is outlined in Table 3
while Table 4 outlines the corresponding byte write and byte
read protocol. The slave receiver address is 11010010 (D2h).
T
Table 2. Command Code Definition
Bit
Description
7
0 = Block read or block write operation, 1 = Byte read or byte write operation
(6:0)
Byte offset for byte read or byte write operation. For block read or block write operations, these bits should be
'0000000'
Table 3. Block Read and Block Write Protocol
Block Write Protocol
Block Read Protocol
Description
Bit
1
Description
Bit
1
Start
Start
2:8
9
Slave address – 7 bits
Write = 0
2:8
9
Slave address – 7 bits
Write = 0
10
Acknowledge from slave
10
Acknowledge from slave
11:18
Command Code – 8 Bit
'00000000' stands for block operation
11:18
Command Code – 8 Bit
'00000000' stands for block operation
19
20:27
28
Acknowledge from slave
Byte Count – 8 bits
Acknowledge from slave
Data byte 1 – 8 bits
Acknowledge from slave
Data byte 2 – 8 bits
Acknowledge from slave
......................
19
20
Acknowledge from slave
Repeat start
21:27
28
Slave address – 7 bits
Read = 1
29:36
37
29
Acknowledge from slave
Byte count from slave – 8 bits
Acknowledge from master
Data byte from slave – 8 bits
Acknowledge from master
Data byte from slave – 8 bits
Acknowledge from master
Data byte N from slave – 8 bits
Acknowledge from master
Stop
38:45
46
30:37
38
....
39:46
47
....
Data Byte (N–1) –8 bits
Acknowledge from slave
Data Byte N –8 bits
Acknowledge from slave
Stop
....
48:55
56
....
....
....
....
....
....
Rev 1.0,November 21, 2006
Page 5 of 18
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