
4-14
PowerPC Microprocessor Family: The Bus Interface for 32-Bit Microprocessors
Table 4-5 and Table 4-6 give a general sense of the basic behavior of the processor. For
example, it does not address noncacheable or write-through cases, nor does it completely
describe the exact mechanisms for the operations described.For a complete listing of cache
coherency operations, see Appendix E, “Coherency Action Tables.”
4.6.2 TLB Invalidate Entry Instruction Processing
Executing a
tlbie
instruction causes a processor to invalidate any TLB entry that
corresponds to that instruction’s effective address. It also causes a TLBIE operation to be
broadcast onto the bus (except on the 603).
4.6.2.1 TLBIE Bus Operation
The TLBIE bus operation is an address-only transaction. The address that is transmitted
contains at least bits EA[12–19] in their correct bit positions. Processors that receive this
transaction use the address to index into their TLB(s) and invalidate an entire congruence
class. Any other device that implements its own TLB must process the TLBIE bus
operation.
To avoid system deadlock conditions, devices that process TLBIE bus operations must start
the operation only after the bus operation has been completed without an ARTRY response.
Because participating devices take an unspecified amount of time to perform their
invalidations, completion of the entire invalidation sequence is not guaranteed until
completion of a synchronization operation, as described in Section 4.7, “Descriptions of
Bus Transactions and Snoop Responses.” The 601 uses the
sync
instruction to synchronize
TLBIE operations; the 604 uses
tlbsync
.
4.7 Descriptions of Bus Transactions and Snoop
Responses
This is a summary of bus transactions and snoop responses. Causes and effects of these
operations are given in Appendix E, “Coherency Action Tables.”
4.7.1 General Comments on 60x Snooping
When 60x processors are not bus master, they monitor bus traffic and perform cache and
memory queue snooping as appropriate. Snooping is triggered by the receipt of a qualified
snoop request, as indicated by the simultaneous assertion of the TS and GBL.
Processors drive two snoop status signals, ARTRY and SHD, in response to qualified snoop
requests. These signals provide information about the state of the addressed block with
respect to 60x for the current bus operation. These signals are described in more detail
earlier in this document. The following additional comments apply:
Any bus transaction that does not have GBL asserted can be ignored by all bus
snoopers. Such transactions are ignored by 60x processors (except 603). For more
information, refer to Chapter 8, “System Interface Operation,” in the
PowerPC
603e
RISC Microprocessor User’s Manual
.