636
March 2002 Release
1-800-255-7778
Virtex-II Pro™ Platform FPGA Documentation
Chapter 11:
Instruction Set
R
The processor does not automatically wait for the ICDBDR to be updated by an
icread
before executing a
mfspr
that reads the ICDBDR. An
isync
instruction should be inserted
between the
icread
and the
mfspr
used to access the ICDBDR.
Pseudocode
EA
←
(
r
A|0) + (
r
B)
if ((CCR0[CIS]
=
0)
∧
(CCR0[CWS]
=
0))
then (ICDBDR)
←
(instruction-cache word, way A)
if ((CCR0[CIS]
=
0)
∧
(CCR0[CWS]
=
1))
then (ICDBDR)
←
(instruction-cache word, way B)
if ((CCR0[CIS]
=
1)
∧
(CCR0[CWS]
=
0))
then (ICDBDR)
←
(instruction-cache tag, way A)
if ((CCR0[CIS]
=
1)
∧
(CCR0[CWS]
=
1))
then (ICDBDR)
←
(instruction-cache tag, way B)
Registers Altered
•
ICDBDR.
Exceptions
•
Data TLB miss—if data relocation is enabled and a valid translation-entry
corresponding to the EA is not found in the TLB.
•
Program—Attempted execution of this instruction from user mode.
This instruction is considered a “load” with respect to the above data-access exceptions. It
can cause data TLB-miss exceptions related to the EA even though the instruction is not
address specific (multiple addresses are selected by a single EA). This instruction cannot
cause data-storage exceptions. This instruction does not cause data address-compare
(DAC) debug exceptions.
Instruction-storage exceptions and instruction TLB-miss exceptions are associated with
instruction
fetching
, not with instruction
execution
. Exceptions that occur during the
execution of instruction-cache operations cause data-storage exceptions and data TLB-
miss exceptions.
Execution of any of the following invalid-instruction forms results in a boundedly-
undefined result rather than a program exception:
•
Reserved bits containing a non-zero value.
Compatibility
This instruction is implementation specific and is not guaranteed to be supported by other
PowerPC processors.
27
V
Valid
0—Cacheline is not valid.
1—Cacheline is valid.
Contains a copy of the cache-line valid bit.
28:30
Reserved
31
LRU
Least-Recently Used
0—Way A is least-recently
used.
1—Way B is least-recently
used.
Contains the LRU bit for the congruence class associated with the
cacheline.
Bit
Name
Function
Description
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