Exceptions
MPC885 PowerQUICC Family Reference Manual, Rev. 2
6-6
Freescale Semiconductor
6.1.2.3
DSI Exception (0x00300)
DSI exceptions are never generated by the hardware. Software may branch to this location as a result of
either implementation specific DTLB error interrupt or implementation specific STLB miss interrupt.
6.1.2.4
ISI Exception (0x00400)
ISI exceptions is never generated by the hardware. The software may branch to this location as a result of
an implementation-specific ITLB error interrupt.
6.1.2.5
External Interrupt Exception (0x00500)
In the MPC885 the external interrupt is generated by the on-chip interrupt controller. It is software
acknowledged and maskable by MSR[EE], which hardware clears automatically to disable external
interrupts when any exception is taken.
When an external interrupt is detected, program execution continues until all previous instructions retire
from the completion queue and the exception is assigned to the instruction last entry in the completion
queue (at point B in
Table 6-19
). However, the following conditions must be met before the instruction at
the end of the queue can retire.
•
The instruction must be completed without exception
•
The instruction must either be a mtspr, mtmsr, rfi, a memory reference, or a memory- or
cache-control instruction.
Instructions not fitting these criteria are discarded along with any execution results. After the exception
handler completes, execution resumes with the first instruction that was discarded. If all the instructions
in the completion queue were allowed to complete, execution at the end of the exception handler resumes
with the next instruction. External exception latency depends on the time required to reference memory.
The measurement is equal to the time taken for one of the following three events, in addition to the interval
from B to E, as shown in
Table 6-19
.
•
Longest load/store multiple/string instruction used
•
One bus cycle for aligned access
•
Two bus cycles for unaligned access
System-level exception latency can be longer than the interval from B to E. If an instruction ahead of the
exception-causing instruction also generates an exception, that exception is recognized first. If it is
important to minimize exception latency, exception handlers should save the machine context and reenable
exceptions as quickly as possible so pending external exceptions are handled quickly.
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...