CY28378 Cypress Semiconductor, CY28378 Datasheet - Page 10

• Manufacturer Part Number: CY28378
• Description: FTG for Pentium 4 and Intel 845 Series Chipset
• Manufacturer: Cypress Semiconductor

Document #: 38-07519 Rev. **
Byte 12
Byte 13
Byte 14
Watchdog Self Recovery Sequence
This feature is designed to allow the system designer to
change frequency while the system is running and reboot the
operation of the system in case of a hang up due to the
frequency change.
When the system sends an SMBus command requesting a
frequency change through the Dial-a-Frequency Control
Registers, it must have previously sent a command to the
Watchdog Timer to select which time out stamp the Watchdog
must perform, otherwise the System Self Recovery feature will
not be applicable. Consequently, this device will change
frequency and then the Watchdog timer starts timing.
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Bit
Bit
Bit
@Pup
@Pup
@Pup
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
CPU_FSEL_N6
CPU_FSEL_N5
CPU_FSEL_N4
CPU_FSEL_N3
CPU_FSEL_N2
CPU_FSEL_N1
CPU_FSEL_N0
Pro_Freq_EN
Reserved
CPU_FSEL_M5
CPU_FSEL_M4
CPU_FSEL_M3
CPU_FSEL_M2
CPU_FSEL_M1
CPU_FSEL_M0
Name
Name
Name
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
If Prog_Freq_EN is set, the values programmed in CPU_FSEL_N[6:0] and
CPU_FSEL_M[5:0] will be used to determine the CPU output frequency.
The setting of FS_Override bit determines the frequency ratio for CPU and
other output clocks. 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.
Programmable output frequencies enabled
0 = disabled
1 = enabled
Reserved
If Prog_Freq_EN is set, the values programmed in CPU_FSEL_N[6:0] and
CPU_FSEL_M[5:0] will be used to determine the CPU output frequency.
The setting of FS_Override bit determines the frequency ratio for CPU and
other output clocks. 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.
Meanwhile, the system BIOS is running its operation with the
new frequency. If this device receives a new SMBus command
to clear the bits originally programmed in the Watchdog Timer
bits (reprogram to 0000) before the Watchdog times out, then
this device will keep operating in its normal condition with the
new selected frequency.
The Watchdog timer will also be triggered if you program the
software frequency select bits (FSEL) to a new frequency
selection. If the Watchdog times out before the new SMBus
reprograms the Watchdog Timer bits to (0000), then this
device will send a low system reset pulse, on SRESET# and
changes WD Time-out bit to “1.”
Pin Description
Pin Description
Pin Description
CY28378
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