Interrupts and Exceptions
PowerPC e500 Core Family Reference Manual, Rev. 1
Freescale Semiconductor
5-17
For loads that hit in the cache, parity is enforced at a double-word granularity. So, if a byte load
lies within a double word that contains a parity error, an interrupt is generated. These interrupts do
not occur if the load is on a speculative path and never completes.
L1 cache parity checking is disabled by default and can be enabled by setting L1CSR0[CPE] and
L1CSR1[ICPE].
The e500’s core complex bus (CCB) is also protected by parity. Parity is checked whenever data
is read on either of the two CCB read buses; a machine check interrupt is generated if errors occur.
Parity is also generated whenever data is written on the CCB write bus, giving an opportunity to
identify and report errors when data is cast out of the cache or written with a cache-inhibited or
write-through store. For cache pushes (or castouts), a parity error is generated if there is any bad
parity on the cache line.
For bus reads, a parity error occurs whenever bad data is read on the bus, regardless of whether the
data is ever used. CCB read bus parity checking is disabled by default and is enabled by setting
HID1[R1DPE] and HID1[R2DPE].
Table 5-10
is an expanded list of the scenarios listed above. For each scenario, there is a list of
what kind of machine check error can occur as indicated by the MCSR bit that is set. For each
condition, the table provides comments about recoverability, whether the MCAR has the address
of the bad data, whether the exception is precise, and how far corrupted data can go into the GPRs,
cache, or memory.
Table 5-10. Parity Error Exception Scenarios
Scenario
MCSR Bit
Description
MCSRR0 and MCAR Values
Comments
Load
(cache hit)
DCPERR
Detection of a data cache parity
error
MCSRR0 has the instruction
address of the failing load
instruction.
MCAR is not set.
Data does not get into
GPR.
Store
(cache hit)
No cases to consider
Load (cache
miss or cache
inhibited)
BUS_RAERR Address bus error
MCSRR0 points to some
instruction near the failing load.
MCAR is set to an address on the
cache line with the error.
Data does not get into
GPR.
Line-fill data does not get
into L1 cache (if
cacheable).
BUS_RBERR Read data bus error
BUS_RPERR Detection of a read data bus parity
error
Store
(cache miss)
BUS_RAERR Address bus error
MCSRR0 points to some
instruction after the failing store.
(It is not particularly meaningful.)
MCAR is set to an address on the
cache line with the error.
Line-fill data does not get
into L1 cache. (Stores to
that line may be lost.)
BUS_RBERR Read data bus error
BUS_RPERR Detection of read data bus parity
error
Store (cache-
inhibited or
write-through)
BUS_WAERR Address bus error
MCSRR0 points to some
instruction near the failing store.
(It is not particularly meaningful.)
MCAR is set to an address on the
cache line with the error.
The system has enough
information to prevent
memory corruption.
BUS_WBERR Write data bus error signaled by
assertion of
core_wr_errin_b input
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