W233 Cypress Semiconductor Corp., W233 Datasheet - Page 6

• Manufacturer Part Number: W233
• Description: Spread Spectrum FTG For Via Mobile K7 Chipset
• Manufacturer: Cypress Semiconductor Corp.

Serial Data Interface
The W233 features a two-pin, serial data interface that can be
used to configure internal register settings that control partic-
ular device functions. Upon power-up, the W233 initializes
with default register settings, therefore the use of this serial
data interface is optional. The serial interface is write-only (to
the clock chip) and is the dedicated function of device pins
SDATA and SCLOCK. In motherboard applications, SDATA
and SCLOCK are typically driven by two logic outputs of the
Table 2. Serial Data Interface Control Functions Summary
Table 3. Byte Writing Sequence
Document #: 38-07250 Rev. **
Clock Output Disable
CPU Clock Frequency
Selection
Spread Spectrum
Enabling
Output Three-state
(Reserved)
Byte Sequence
Control Function
10
11
1
2
3
4
5
6
7
8
9
Slave Address
Command
Code
Byte Count
Data Byte 0
Data Byte 1
Data Byte 2
Data Byte 3
Data Byte 4
Data Byte 5
Data Byte 6
Data Byte 7
Byte Name
Any individual clock output(s) can be disabled. Dis-
abled outputs are actively held LOW.
Provides CPU/PCI frequency selections through
software. Frequency is changed in a smooth and
controlled fashion.
Enables or disables spread spectrum clocking.
Puts clock output into a high impedance state.
Reserved function for future device revision or pro-
duction device testing.
11010010
Don’t Care
Don’t Care
Refer to Table 4 The data bits in Data Bytes 0–7 set internal W233 registers that control
Bit Sequence
PRELIMINARY
Description
Commands the W233 to accept the bits in Data Bytes 0–6 for internal
register configuration. Since other devices may exist on the same com-
mon serial data bus, it is necessary to have a specific slave address for
each potential receiver. The slave receiver address for the W233 is
11010010. Register setting will not be made if the Slave Address is not
correct (or is for an alternate slave receiver).
Unused by the W233, therefore bit values are ignored (“Don’t Care”).
This byte must be included in the data write sequence to maintain proper
byte allocation. The Command Code Byte is part of the standard serial
communication protocol and may be used when writing to another ad-
dressed slave receiver on the serial data bus.
Unused by the W233, therefore bit values are ignored (“Don’t Care”).
This byte must be included in the data write sequence to maintain proper
byte allocation. The Byte Count Byte is part of the standard serial com-
munication protocol and may be used when writing to another addressed
slave receiver on the serial data bus.
device operation. The data bits are only accepted when the Address
Byte bit sequence is 11010010, as noted above. For description of bit
control functions, refer to Table 4, Data Byte Serial Configuration Map.
chipset. 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 manage-
ment functions. Table 2 summarizes the control functions of
the serial data interface.
Operation
Data is written to the W233 in eleven bytes of eight bits each.
Bytes are written in the order shown in Table 3.
Unused outputs are disabled to reduce EMI
and system power. Examples are clock out-
puts to unused PCI slots.
For alternate microprocessors and power
management options. Smooth frequency tran-
sition allows CPU frequency change under
normal system operation.
For EMI reduction.
Production PCB testing.
No user application. Register bit must be writ-
ten as 0.
Byte Description
Common Application
Page 6 of 16
W233