CY28349
Table 4. Frequency Selection Table
Input Conditions
Output Frequency
PLL Gear
Constants
(G)
FS4
FS3
FS2
FS1
FS0
SEL4
SEL3
SEL2
SEL1
SEL0
CPU
167.4
170.0
175.0
180.0
185.0
190.0
166.8
100.2
133.6
200.4
166.6
100.0
200.0
133.3
3V66
66.9
68.0
70.0
72.0
74.0
76.0
66.7
66.8
66.8
66.8
66.6
66.6
66.6
66.6
PCI
33.5
34.0
35.0
36.0
37.0
38.0
33.4
33.4
33.4
33.4
33.3
33.3
33.3
33.3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
1
1
1
1
0
0
0
0
1
1
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
48.00741
The Watchdog Timer and Recovery Output Frequency
features allow users to implement a recovery mechanism
when the system hangs or gets unstable. System BIOS or
other control software can enable the Watchdog Timer before
they attempt to make a frequency change. If the system hangs
and a Watchdog Timer time-out occurs, a system reset will be
generated and a recovery frequency will be activated.
Programmable Output Frequency, Watchdog
Timer and Recovery Output Frequency
Functional Description
The Programmable Output Frequency feature allows users to
generate any CPU output frequency from the range of 50 MHz
to 248 MHz. Cypress offers the most dynamic and the simplest
programming interface for system developers to utilize this
feature in their platforms.
All of the related registers are summarized in Table 5.
Table 5. Register Summary
Name
Description
Pro_Freq_EN
Programmable output frequencies enabled
0 = Disabled (default)
1 = Enabled
When it is disabled, the operating output frequency will be determined by either the latched value of
FS[4:0] inputs or the programmed value of SEL[4:0]. If FS_Override bit is clear, latched FS[4:0] inputs
will be used. If FS_Override bit is set, programmed value of SEL[4:0] will be used.
When it is enabled, the CPU output frequency will be determined by the programmed value of
CPUFSEL_N, CPUFSEL_M and the PLL Gear Constant. The program value of FS_Override, SEL[4:0]
or the latched value of FS[4:0] will determine the PLL Gear Constant and the frequency ratio between
CPU and other frequency outputs
FS_Override
When Pro_Freq_EN is cleared or disabled,
0 = Select operating frequency by FS input pins (default)
1 = Select operating frequency by SEL bits in SMBus control bytes
When Pro_Freq_EN is set or enabled,
0 = Frequency output ratio between CPU and other frequency groups and the PLL Gear Constant are
based on the latched value of FS input pins (default)
1 = Frequency output ratio between CPU and other frequency groups and the PLL Gear Constant are
based on the programmed value of SEL bits in SMBus control bytes
ROCV_FREQ_SEL
ROCV_FREQ_SEL determines the source of the recover frequency when a Watchdog timer time-out
occurs. The clock generator will automatically switch to the recovery CPU frequency based on the
selection on ROCV_FREQ_SEL.
0 = From latched FS[4:0]
1 = From the settings of ROCV_FREQ_N[7:0] & ROCV_FREQ_M[6:0]
Rev 1.0,November 24, 2006
Page 13 of 20
SPECTRALINEAR [ SPECTRALINEAR INC ]
