Cypress CY25822-2 manual Pin Description, Serial Data Interface, Data Protocol

CY25822-2

Pin Description

Pin No.	Pin Name	Pin Type	Pin Description
1	CLKIN	Input	48-MHz or 66-MHz Clock Input.
2	VDD	Power	Power Supply for PLL and Outputs.
3	GND	Ground	Ground for Outputs.
4	CLKOUT	Output	48-MHz or 66-MHz Spread Spectrum Clock Output.
5	REFOUT	Output	Non-spread Spectrum Reference Clock Output.
6	SDATA	I/O	I2C-compatible SDATA.
7	SCLOCK	Input	I2C-compatible SCLOCK.
8	PWRDWN#	Output	LVTTL Input for PowerDown# Active Low.

Serial Data Interface

To enhance the flexibility and function of the clock synthesizer,

atwo-signal serial interface is provided. Through the Serial Data Interface, various device functions such as individual clock output buffers, etc., 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 can also be used during system operation for power management functions.

Table 1. Command Code Definition

Data Protocol

The clock driver serial protocol accepts byte write, byte read, block write, and block read operation 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 individual indexed bytes. The offset of the indexed byte is encoded in the command code, as described in Table 1.

The block write and block read protocol is outlined in Table 2 while Table 3 outlines the corresponding byte write and byte read protocol.The slave receiver address is 11010100 (D4h).

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 2. Block Read and Block Write Protocol
		Block Write Protocol			Block Read Protocol
Bit		Description		Bit	Description
1		Start		1	Start
2:8		Slave address – 7 bits		2:8	Slave address – 7 bits
9		Write = 0		9	Write = 0
10		Acknowledge from slave		10	Acknowledge from slave
11:18		Command Code – 8 bits		11:18	Command Code – 8 bits
		'00000000' stands for block operation			'00000000' stands for block operation
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
....		......................		39:46	Data byte from slave – 8 bits
....		Data Byte (N–1) –8 bits		47	Acknowledge
....		Acknowledge from slave		48:55	Data byte from slave – 8 bits
Document #: 38-07531 Rev. **					Page 2 of 9

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