Diversified Technology CPB-4612, Руководство по настройке и обслуживанию

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7.1 Watchdog Timer Overview
The watchdog timer is implemented by using the 6300ESB ICH integrated watchdog timer. The primary
function of the watchdog timer is to monitor the cPB-4612’s operation and take corrective action if the
software fails to function as programmed. The major features of the watchdog timer are:
•
Two-stage operation (meaning that it can be enabled to produce a system management interrupt
[SMI] or an IRQ (APIC 1, INT 10) before it generates a reset)
•
Enabled and disabled through software control
• Armed and strobed through software control
The watchdog timer drives the First and Second Stages as follows:
1. The watchdog times out (First Stage) after a selected timeout interval.
2. SMI or IRQ is driven high.
3. A hard reset occurs (Second Stage) after a selected timeout interval.
The watchdog timer can have a range from 1µs to 10 minutes. The timer uses a 35 bit down counter. The
counter is loaded with the first preload register. The timer is then enabled and it starts counting down.
This is called the first stage. If the counter reaches zero before being reloaded, the watchdog timer
generates an internal interrupt. The counter is then loaded with the second preload register and starts
counting down. This is called the second stage. If the counter reaches zero before being reloaded, the
watchdog timer drives the WDT_TOUT pin low until the system is reset.
More information can be obtained from the Intel 6300ESB Datasheet. The "Intel 855GME Chipset" topic
in Appendix D provides a link to the 6300ESB datasheet.
7.2 PCI Configuration Registers
The two stage watchdog timer controller appears in PCI config space at Bus:0 Dev:29 Func:4. The
following registers are the primary PCI registers to control the watchdog timer.
7.2.1 Base Address Register (10h)
Offset: 10h
Default Value: 00000000h
Size: 32 bits
Attribute: R/W
Bit Description
31:4
Base Address
Base address points to the memory mapped region
3
Prefetchable
Hard-wired to 0
2:1
Type
Hard-wired to 00
0
Resource Type Indicator
Hard-wired to 0