參數(shù)資料
型號(hào): CY25245
英文描述: Clocks and Buffers
中文描述: 時(shí)鐘和緩沖器
文件頁(yè)數(shù): 5/11頁(yè)
文件大?。?/td> 116K
代理商: CY25245
CY25245
Document #: 38-07124 Rev. *A
Page 5 of 11
Table 3. Serial Data Interface Control Functions Summary
Writing Data Bytes
Each bit in Data Bytes 0
7 control a particular device function
except for the
reserved
bits which must be written as a logic
0. Bits are written MSB (most significant bit) first, which is bit 7.
Table 5
gives the bit formats for registers located in Data Bytes
0
7.
Control Function
Clock Output Disable Any individual clock output(s) can be disabled.
Disabled outputs are actively held LOW.
Description
Common Application
Unused outputs are disabled to reduce EMI and
system power. Examples are clock outputs to unused
PCI slots.
For alternate microprocessors and power
management options. Smooth frequency transition
allows CPU frequency change under normal system
operation.
For EMI reduction.
CPU Clock Frequency
Selection
Provides CPU/PCI frequency selections through
software. Frequency is changed in a smooth and
controlled fashion.
Spread Spectrum
Enabling
Output three-state
(Reserved)
Enables or disables spread spectrum clocking.
Puts clock output into a high-impedance state.
Reserved function for future device revision or
production device testing.
Production PCB testing.
No user application. Register bit must be written as 0.
Table 4. Byte Writing Sequence
Byte
Sequence
1
Byte Name
Slave Address
Bit Sequence
11010010
Byte Description
Commands the CY25245 to accept the bits in Data Bytes 0
6 for internal register
configuration. Since other devices may exist on the same common serial data
bus, it is necessary to have a specific slave address for each potential receiver.
The slave receiver address for the CY25245 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 CY25245, 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 addressed slave receiver on the serial
data bus.
Unused by the CY25245, 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 communication protocol and may
be used when writing to another addressed slave receiver on the serial data bus.
Refer to
Table 5
The data bits in Data Bytes 0
7 set internal CY25245 registers that control 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 5
, Data Byte Serial Configuration Map.
2
Command Code Don
t Care
3
Byte Count
Don
t Care
4
5
6
7
8
9
Data Byte 0
Data Byte 1
Data Byte 2
Data Byte 3
Data Byte 4
Data Byte 5
Data Byte 6
Data Byte 7
10
11
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