
176
Registers
Chapter 4
AMD-8111 HyperTransport I/O Hub Data Sheet
24674
Rev. 3.00
April 2003
AMD Preliminary Information
Watchdog Timer Control/Status Register
WDT00
Default:
0000 0008h.
Attribute:
see below.
Watchdog Timer Count Register
WDT08
Default:
0000 0000h.
Attribute:
see below.
4.4.7
High Precision Event Timer Registers
The HPET Registers are non-enumerable memory mapped I/O registers. The base address is
controlled by DevB:0xA0. All registers can be accessed by 32 bit memory accesses.
Bits
31:8
7
Description
Read-only.
WTRIG. Watchdog Trigger
. Read-write. Setting this bit triggers the watchdog timer to start a new
count interval, counting down from the value that was last written to the Watchdog Count Register.
This bit always reads as zero. Setting this bit has no effect when DevB:0xA8[WDTHALT] is set or
RSTOP is cleared.
Read-only.
WDA_ALIAS. Watchdog Disable Alias
. Read-only. This bit re
fl
ects the state of the watchdog timer
hardware and is an alias of DevB:0xA8[WDTHALT]. 1 = Watchdog timer functionality disabled.
0=Watchdog timer functionality enabled.
WACT. Watchdog Action
. Read-write. This bit determines the action to be taken when the watchdog
timer expires. 0 = system reset; 1 = system power off.
WFIR. When set, the watchdog timer expired and caused the current restart
.Read-write. This bit
is cleared for any restart that is not caused by the watchdog timer
fi
ring. If the Watchdog Action bit is
set to 1 (system power off) and the watchdog timer
fi
res, forcing a shutdown, the bit will be cleared on
the next power up.
RSTOP.
Read-write. This bit is used to control or indicate whether the watchdog timer is in the
Running or Stopped state.
1 = Watchdog timer is in the Running state. 0 = Watchdog timer is in the Stopped state.
If the watchdog timer is in the Stopped state and a 1 is written to bit 0, the watchdog timer moves to
the Running state but a count interval is not started until a 1 is written to bit 7.
If the watchdog timer is in the Running state, writing a 1 to bit 0 has no effect.
6:4
3
2
1
0
Bits
31:16 Read-only.
15:0
WCD. Watchdog Count Data
. Read-write. This de
fi
nes the countdown time for the counter in
seconds. Reading this register results in the current counter value. Writing to the register has no
effect until a one is written to the watchdog trigger bit of the Watchdog Control/Status Register. All bits
have to be written by one access.
Description