PRELIMINARY
CY28443
Document #: 38-07716 Rev *C
Page 4 of 25
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 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).
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
Bit
Description
Bit
Description
1
Start
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
(Skip this step if I2C_EN bit set)
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
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