![Xilinx Virtex-II Pro PPC405 Скачать руководство пользователя страница 188](http://html1.mh-extra.com/html/xilinx/virtex-ii-pro-ppc405/virtex-ii-pro-ppc405_user-manual_3410279188.webp)
496
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 7:
Exceptions and Interrupts
R
Persistent Exceptions and Interrupt Masking
When certain exceptions are recognized by the processor, system software can prevent the
corresponding interrupt from occurring by disabling, or
masking
, the interrupt. In general,
disabling an interrupt only delays its occurrence. The processor continues to recognize the
exception. When software re-enables (unmasks) the interrupt, the interrupt occurs. Such
exceptions are referred to as
persistent
exceptions.
An persistent exception normally sets a status bit in a specific register associated with the
exception mechanism. The only way for software to prevent the interrupt from occurring is
to clear the exception-status bit before unmasking (enabling) the interrupt. Likewise, the
interrupt handler must clear the exception-status bit to prevent the interrupt from
reoccurring, should it be re-enabled upon exiting the interrupt handler.
The following exceptions are persistent and their corresponding interrupts can be
disabled:
10
Program
Attempted execution of:
•
An illegal instruction.
•
Unimplemented floating-point instructions.
•
Unimplemented auxiliary-processor instructions.
•
A privileged instruction from user mode.
•
Execution of a trap instruction that satisfies the trap conditions.
System call
Execution of the
sc
instruction.
FPU unavailable
Attempted execution of an implemented floating-point instruction when
MSR[FP]=0. Not implemented by the PPC405D5.
APU unavailable
Attempted execution of an implemented auxiliary-processor instruction
when MSR[AP]=0. Not implemented by the PPC405D5.
11
Data TLB Miss
Attempted access of data from an address with no valid, matching page
translation loaded in the TLB (virtual mode only).
12
Data storage—No access.
In user mode, attempted access of data from a memory address with no-
access-allowed zone protection (virtual mode only).
13
Data storage—Read-only.
Attempted data write (store) into a read-only memory address (virtual
mode only).
Data storage—User defined.
Attempted data write (store) into a memory address with the U0 storage
attribute set to 1, when U0 exceptions are enabled.
14
Alignment
Attempted execution of:
•
dcbz
to a non-cacheable or write-though cacheable address.
•
lwarx
or
stwcx.
to an address that is not word aligned.
•
dcread
to an address that is not word aligned (privileged mode only).
15
Debug—Branch taken.
Branch taken (BT) debug event.
Debug—Data-address compare.
Data-address compare (DAC) debug event.
Debug—Data-value compare.
Data-value compare (DVC) debug event.
Debug—Instruction completion.
Instruction completion (IC) debug event.
Debug—Trap instruction.
Trap instruction (TDE) debug event.
16
External
Noncritical-interrupt input signal is asserted.
17
Fixed-interval timer
Fixed-interval timer time-out.
18
Programmable-interval timer
Programmable-interval timer time-out.
Table 7-2:
Interrupt Priority for Simultaneous Exceptions
(Continued)
Priority
Exception
Cause
Содержание Virtex-II Pro PPC405
Страница 1: ...R Volume 2 a PPC405 User Manual Virtex II Pro Platform FPGA Developer s Kit March 2002 Release...
Страница 14: ...322 www xilinx com March 2002 Release 1 800 255 7778 Virtex II Pro Platform FPGA Documentation Preface R...
Страница 252: ...560 www xilinx com March 2002 Release 1 800 255 7778 Virtex II Pro Platform FPGA Documentation R...
Страница 260: ...568 www xilinx com March 2002 Release 1 800 255 7778 Virtex II Pro Platform FPGA Documentation R...
Страница 562: ...870 www xilinx com March 2002 Release 1 800 255 7778 Virtex II Pro Platform FPGA Documentation R...