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Release 1.0, 1 July 2002 F. Chapter P Error Handling
171
TABLE P-14
defines each instruction end-method after an
ADE
trap.
P.4.4 Expected Software Handling of
ADE
Tr a p
The expected software handling of an
ADE
trap is described by the pseudo C code
below. The main purpose of this flow is to recover from the following errors as much
as possible:
■
An error in the CPU internal RAM or register file
■
An error in the accumulator
■
An error in the CPU internal temporary registers and data bus
TABLE P-14
Instruction End-Method After
async_data_error
Exception
Precise Retryable But Not Precise Not Retryable
Instructions executed after
the last
ADE
,
IAE
, or
DAE
trap and before the trapped
instruction referenced by
TPC.
Ended (Committed).
The instructions without
UGE
complete as defined in the architecture. The
instruction with
UGE was unpredictable value to its output (destination register or,
in the case of a store instruction, destination memory location).
The trapped instruction
referenced by TPC
Not executed. The output of the instruction is
incomplete.
Part of the output may be
changed, or the invalid value
may be written to the instruction
output. However, the
modification to the invalid target
that is not defined as instruction
output is not executed.
The following modifications are
not executed:
• Store to the cacheable area
including cache.
• Store to the noncacheable area.
• Output to the source register of
the instruction (destructive
overlap)
The output of the instruction is
incomplete.
Part of the output may be
changed, or the invalid value
may be written to the instruction
output. However, the
modification to the invalid target
that is not defined as instruction
output is not executed.
A store to an invalid address is
not executed. (Store to a valid
address with uncorrected data
may be executed.)
Instructions to be executed
after the instruction
referenced by TPC
Not executed. Not executed. Not executed.
The possibility of resuming
the trapped program by
executing the RETRY
instruction to the %tpc
when the trapped program
is not damaged at the
single-
ADE
trap
Possible. Possible. Impossible.