PRELIMINARY
C9926
Low EMI Clock Generator for Intel 133MHz/ 2DIMM Chipset Systems
Serial Control Registers
NOTE: The Pin# column lists the affected pin number where applicable. The @Pup column gives the state at true
power up. Bytes are set to the values shown only on true power up.
Following the acknowledge of the Address Byte, two additional bytes must be sent:
1) “Command Code “ byte, and
2) “Byte Count” byte.
Although the data (bits) in these two bytes are considered “don’t care”; they must be sent and will be acknowledged.
After the Command Code and the Count bytes have been acknowledged, the following sequence (Byte 0, Byte 1, and
Byte2) will be valid and acknowledged.
Byte 0: CPU Clock Register (1=Enable, 0=Disable)
Byte 1: SDRAM Clock Register (1=Enable, 0=Disable)
Bit
7
6
5
4
@Pup
Pin#
Description
Bit
7
6
5
4
3
2
1
0
@Pup
Pin#
Description
RESERVED (drive to “0”)
RESERVED (drive to “0”)
SDRAM5
SDRAM4
SDRAM3
SDRAM2
SDRAM1
SDRAM0
0
0
0
0
0
-
-
-
-
-
SEL3 frequency selector
SEL2 frequency selector
SEL1 frequency selector
SEL0 frequency selector
1 = Spread Spectrum Enabled
0 = Spread Spectrum Disabled
DOT
1
1
1
1
1
1
1
1
-
-
-
-
-
-
-
-
3
2
1
0
1
1
0
27
26
-
USB
High enables bit(7:4) selectors.
Byte 3: Reserved Register
Byte 2: SDRAM Clock Register (1=Enable, 0=Disable)
Bit
7
6
5
4
3
2
1
@Pup
Pin#
-
-
-
-
-
-
28
Description
RESERVED
High puts the device in TEST mode.
RESERVED
RESERVED
RESERVED
RESERVED
1 enables std. Functionality TS#/PD#
0 enables TS# only
0 = SDRAM runs at 100MHz
1= SDRAM runs at 133.3MHz
Bit
7
@Pup
Pin#
10
-
Description
3V66-2
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
6
5
4
3
2
1
0
RESERVED (drive to “0”)
RESERVED (drive to “0”)
SDRAM8
SDRAM7
SDRAM6
-
29
30
31
13
-
PCI1
RESERVED
0
0
-
Byte 4: PCI Clock Register (1=Enable, 0=Disable)
Byte 5: SSCG Control Register
Bit
7
@Pup
Pin#
-
-
Description
RESERVED
RESERVED
RESERVED
RESERVED (drive to “0”)
RESERVED (drive to “0”)
PCI4
Bit
7
@Pup
Pin#
Description
0
0
0
1
1
1
1
1
0
0
0
0
0
0
0
0
-
-
-
-
-
-
-
-
Spread Mode (0=down, 1=center)
Selects spread bandwidth. Ref. Table 4
Selects spread bandwidth. Ref. Table 4
RESERVED
6
6
5
4
5
-
4
-
3
-
3
RESERVED
2
1
0
18
17
14
2
RESERVED
PCI3
PCI2
1
RESERVED
0
RESERVED
Cypress Semiconductor Corporation
525 Los Coches St.
Document#: 38-07070 Rev. **
5/4/2001
Milpitas, CA 95035. Tel: 408-263-6300, Fax: 408-263-6571
http://www.cypress
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