O.2.1 RED_state

Once the processor enters RED_state for any reason except when a power-on reset (POR) is performed, the software should not attempt to return to execute_state; if software attempts a return, then the state of the processor is unpredictable.

When the processor processes a reset or a trap that enters RED_state, it takes a trap at an offset relative to the RED_state trap table (RSTVaddr); in the processor this is at virtual address VA = FFFFFFFFF000000016 and physical address

PA = 000007FFF000000016.

The following list further describes the processor behavior upon entry into

RED_state, and during RED_state:

Whenever the processor enters RED_state, all fetch buffers are invalidated.

When the processor enters RED_state because of a trap or reset, the DCUCR register is updated by hardware to disable several hardware features. Software must set these bits when required (for example, when the processor exits from

RED_state).

When the processor enters RED_state not because of a trap or reset (that is, when the PSTATE.RED bit has been set by WRPR), these register bits are unchanged—unlike the case above. The only side effect is the disabling of the instruction MMU.

When the processor is in RED_state, it behaves as if the IMMU is disabled (DCUCR.IM is clear), regardless of the actual values in the respective control register.

Caches continue to snoop and maintain coherence while the processor is in

RED_state.

O.2.2 error_state

The processor enters error_state when a trap occurs and TL = MAXTL (5) or when the second watchdog timeout has occurred.

On the normal setting, the processor immediately generates a watchdog reset trap (WDR) and transitions to RED_state. Otherwise, the OPSR (Operating Status Register) specifies the stop on error_state, that is, the processor does not generate a watchdog reset after error_state transition and remains in the error_state.

140 SPARC JPS1 Implementation Supplement: Fujitsu SPARC64 V • Release 1.0, 1 July 2002

Page 151
Image 151
Fujitsu Fujitsu SPARC64 V manual PA = 000007FFF000000016