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MPC8240 Integrated Processor User’s Manual
Cache Implementation
Unlike entire cache locking, invalid entries in a locked way are accessible and available for
data placement. As hits to the cache fill invalid entries within a locked way, the entries
become valid and locked. This behavior differs from entire cache locking where nothing is
placed in the cache, even if invalid entries exist in the cache. Unlocked ways of the cache
behave normally.
5.4.3 Cache Coherency
The central control unit (CCU) manages the cache coherency within the MPC8240. It
responds to all accesses generated by the processor core and causes the snooping of the
addresses in the internal buffers as necessary. Also, the CCU generates snoop transactions
on the peripheral logic bus to allow the processor to snoop accesses between the PCI
interface and memory. Refer to Chapter 7, “PCI Bus Interface,” for more detailed
information about the internal address and data buffers in the MPC8240.
5.4.3.1 CCU Responses to Processor Transactions
The processor core generates various types of read and write accesses as well as
address-only transactions. Table 5-5 shows all the types of internal transactions performed
by the processor core and the CCU responses.
Table 5-5. CCU Responses to Processor Transactions
Processor Transaction
CCU Response
Read
Directs read to appropriate interface
Read-with-intent-to-modify
Directs read to appropriate interface
Read atomic
Directs read to appropriate interface
Read-with-intent-to-modify-atomic
Directs read to appropriate interface
Write-with-flush
Directs write to appropriate interface
Write-with-kill
Directs write to appropriate interface
Write-with-flush-atomic
Directs write to appropriate interface
sync
CCU buffers are flushed.
eieio
CCU buffers are flushed.
Kill block (generated by dcbz instruction
when the addressed block has either the E
or M bits set)
CCU buffers are snooped.
icbi
CCU buffers are snooped.
Read-with-no-intent-to-cache
Directs read to appropriate interface
Clean
CCU takes no further action.
Flush
CCU takes no further action.
tlbie
CCU takes no further action.
lwarx, reservation set
CCU takes no further action.
(The MPC8240 does not support atomic
references in PCI memory space.)
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...