Watchdog Function Description
Super Micro Computer, Inc. 03/20/2002

Supported Board: P4SBx, P4DPx

To enable Watchdog function:
	1. BIOS
      For P4SBx:
  BIOS setup  --> Advanced --> Integrated Peripherals  --> Watch Dog Feature
      For P4DPx:
  BIOS setup  --> Advanced --> I/O Device Configuration  --> Watch Dog

This setting enables or disables Watchdog function.  When enabled, the default watchdog timer is set to be 5 minutes (about 4’35”).  It is enough to load and run the OS. The application (service or driver) has to take over the control once OS is running up and before watchdog expires.

      2. JUMPER
      For P4SBx: JP39
      For P4DPx: JP37
This jumper is used for safety.  Closed is enabled. This jumper prevents user enables watchdog in BIOS by accident.

      To enable Watch Dog function, both BIOS and JUMPER must be enabled.

I/O port Description:
Port 0x2e: Register Index
Port 0x2f: Data Input/Output
 
Control Registers Description (all the following registers can be read or written):
	Register 0x07: Control Page Switch. Default value (unknown)
Value == 0x08 --> Switches to Watchdog Control Page

	Register 0x30 (bit 0): Hardware Output Enable/Disable. Default value 0x01
Value == 0x00 --> Disables watchdog. Application may write 0x00 to this register to disable watchdog function on purpose. 
Value == 0x01 --> Enables watchdog. 

	Register 0xf5 (bit 3): Count Mode selection. Default value 0x08
Value == 0x00 -->  Timer counts in unit of second.
Value == 0x08 -->  Timer counts in unit of minute.
When the value in this port counts down to zero, it will reload the value from port 0x461 automatically, and set the flag in port 0x464.  Write any value to this port will cause the value be reloaded from port 0x461.

	Register 0xf6 (bit 0 - bit 7): Watchdog timer. Default value 0x05
Watchdog timer time-out value.
Read: current value in watchdog counter.
Write: pre-defined time-out value.
This register will be re-loaded dependents on the setting of register 0xf7 below.

	Register 0xf7 (bit 6 & bit 7): Watchdog reset control. Default value 0xc0
Bit 7 == 1 --> Watchdog timer is reset upon a mouse interrupt.
Bit 7 == 0 --> Watchdog timer is not affected by mouse interrupt.
Bit 6 == 1 --> Watchdog timer is reset upon a keyboard interrupt.
Bit 6 == 0 --> Watchdog timer is not affected by keyboard interrupt.
Note: although OS crashed, user keeps hitting the keyboard or mouse, then system won’t reboot if bit7 and/or bit6 is set.

In application (service, or driver):
A particular procedure must be executed to control Watchdog every time.
Before control Watchdog:
Out 0x87 to Port 0x2e twice.
Out 0x08 to Register 0x07.
After control Watchdog:
Out 0xaa to Port 0x2e once.

	Periodic Routine:
Write time-out value to register 0xf6 before timer expires.
Examples: (time-out value is 5)
mov	dx, 2eh
mov	al, 87h
out	dx, al
out	dx, al	; write 0x87 to port 0x2e twice
mov	al, 07h
out	dx, al	; set Register 0x07 to Index Port
mov	dx, 2fh
mov	al, 08h
out	dx, al	; switch to Watchdog control page

mov	dx, 2eh
mov	al, f6h
out	dx, al	; set Register 0xf7 to Index Port
mov	dx, 2fh
mov	al, 5h
out	dx, al	; write time-out value 0x5 to Data Port

mov	dx, 2eh
mov	al, aah
out	dx, al	; write 0xaa to port 0x2e once

	Examples:
      	Disable Keyboard Reset Control:
mov	dx, 2eh
mov	al, 87h
out	dx, al
out	dx, al	; write 0x87 to port 0x2e twice
mov	al, 07h
out	dx, al	; set Register 0x07 to Index Port
mov	dx, 2fh
mov	al, 08h
out	dx, al	; switch to Watchdog control page

mov	dx, 2eh
mov	al, f7h
out	dx, al	; set Register 0xf7 to Index Port
mov	dx, 2fh
in	al, dx	; read current setting from Register 0xf7
and	al, 10111111b	; disable keyboard reset flag
out	dx, al	; write back setting to Data Port

mov	dl, 2eh
mov	al, aah
out	dx, al	; write 0xaa to port 0x2e once