Toshiba 2000 Hardware Processing RAS Functions, WDT Circuit and Hardware Reset, RAS Memory

5.2 Hardware Processing RAS Functions

5.2 Hardware Processing RAS Functions

5.2.1WDT Circuit and Hardware Reset

The WDT circuit issues an NMI to the main unit when the WDT counter is not reset within a certain interval (WDT monitoring interval). The WDT monitoring interval can be set up to 500ms x 255 (approximately 2 minutes) in 500ms units.

If an NMI is not accepted within 500ms after a WDT timeout NMI is issued, the system is reset by the hardware reset function.

WDT reset

500ms*N 500ms*N 500ms

NMI request

(recover because reset within 500ms)

NMI issued

Force reset output

Force reset because NMI (WDT) reset is not performed by CPU

<WDT and forced reset time chart>

Important

•Do not enable the suspend function when using the WDT function. This may cause a mal-function.

The suspend function is a power saving method and cannot be used together with the WDT function.

5.2.2RAS Memory

RAS memory is a 64K-byte battery backed non-volatile memory and is used to store NMI events and RAS information. It is also used by the RAS support software to save shutdown information.

RAS memory is designed to be accessed using the I/O space and does not use any memory space.

RAS memory is backed up by the backup battery (Lithium battery) installed inside the main unit.

5.2.3Interrupt Signals

Interrupts detected by RAS board and sent to CPU are classified into NMI events and MI events.

•Examples of NMI events are: WDT timeout, events requiring immediate action such as power failure, system shutdown, and remote input for power control.

•An example of MI event is fan stop.

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