CY28323PVC

Rev 1.0, November 24, 2006

Page 14 of 21

Programmable Output Frequency, Watchdog

Timer and Recovery Output Frequency

Functional Description

The Programmable Output Frequency feature allows users to

generate any CPU output frequency in 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.

The Watchdog Timer and Recovery Output Frequency

features allow users to implement a recovery mechanism

when the system hangs or getting 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.

All 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 the FS_Override bit is clear, latched FS[4:0]

inputs will be used. If the FS_Override bit is set, the 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

CPU_FSEL_N,

CPU_FSEL_M

When Prog_Freq_EN is set or enabled, the values programmed in CPU_FSEL_N[7:0] and

CPU_FSEL_M[6:0] determines the CPU output frequency. The new frequency will start to load

whenever there is an update to either CPU_FSEL_N[7:0] or CPU_FSEL_M[6:0]. Therefore, it is recom-

mended to use Word or Block write to update both registers within the same SMBus bus operation.

The setting of FS_Override bit determines the frequency ratio for CPU, AGP and PIC. When

FS_Override is cleared or disabled, the frequency ratio follows the latched value of the FS input pins.

When FS_Override is set or enabled, the frequency ratio follows 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]

ROCV_FREQ_N[7:0],

ROCV_FREQ_M[6:0]

When ROCV_FREQ_SEL is set, the values programmed in ROCV_FREQ_N[7:0] and

ROCV_FREQ_M[6:0] will be used to determine the recovery CPU output frequency when a

Watchdog timer time-out occurs

The setting of the FS_Override bit determines the frequency ratio for CPU, AGP and PIC. When it is

cleared, the same frequency ratio stated in the Latched FS[4:0] register will be used.

When it is set, the frequency ratio stated in the SEL[4:0] register will be used.

The new frequency will start to load whenever there is an update to either ROCV_FREQ_N[7:0] and

ROCV_FREQ_M[6:0]. Therefore, it is recommended to use Word or Block write to update both registers

within the same SMBus bus operation.

WD_EN

0 = Stop and reload Watchdog Timer

1 = Enable Watchdog Timer. It will start counting down after a frequency change occurs.

WD_TO_STATUS

Watchdog Timer Time-out Status bit

0 = No time-out occurs (READ); Ignore (WRITE)

1 = Time-out occurred (READ); Clear WD_TO_STATUS (WRITE)