C9707
Clock Generator for VIA VT8371/Athlon (K7) Chipset Systems
Preliminary
System Self Recovery Clock Management:
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 I2C command requesting a frequency change through Byte 0, it must also send a command
to byte 6 to select which time out stamp the watch dog must perform. Consequently, this device will change frequency,
and then send out a reset pulse (low) on pin 41, SRESET. The pulse will last 3mS. When the reset signal is removed,
the watch dog timer starts timing. During this time, the system BIOS is running its operation with the new frequency
selected via I2C. If this device receives a new I2C command to remove the bit that was originally programmed in Byte 6
(reprogram byte 6 to 00-Hex), before the watch dog times out, then this device will keep operating in its normal condition
with the new selected frequency. If the watch dog times out before, the new I2C reprograms Byte 6 to 00-Hex, then this
device will re-latch the original (hardware selected) data, regenerate the originally chosen frequency at power up reset
Byte6 to 00-Hex, then sends another system reset pulse. This will allow the system to recover and run with the original
hardware setting frequency.
System running with
originally selected
frequency via
hardware strapping.
No
Frequency will change but System Self
Recover not applicable (no time stamp
selected and byte 6 is still 00-hex).
Receive Frequency
Change Request via I2C
Byte 0?
Yes
No
Is I2C Byte 6, time out
stamp enabled - (byte6 =
00-Hex)?
1) Send another 3mS low pulse on SRESET
2) Relatch original hardware strapping selection
for return to original frequency settings.
3) Reset Byte6 to 00-Hex.
Byte0, bits (7, 6, 5, 4, 2, 1, 0) remain
unchanged. Byte0, bit 3 is reset to 0.
Yes
Change to new frequency
Send out a 3 mS low pulse on SRESET
Start internal watch dog timer.
Yes
Yes
Watch Dog time out?
No
No
No
I2C byte 6 time out
stamp disabled?
Yes
Turn off watch dog timer.
Keep new frequency setting. System running.
Fig. 5
INTERNATIONAL MICROCIRCUITS, INC. 525 LOS COCHES ST.
MILPITAS, CA 95035 TEL: 408-263-6300 FAX 408-263-6571
http://www.imicorp.com
Rev 1.2
4/25/2000
Page 5 of 17
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