Chapter 5. PowerPC Processor Core
5-25
Cache Implementation
5.4.3.2 Processor Responses to PCI-to-Memory Transactions
The CCU controls the data flow between the PCI interface and the memory interface. One
of its functions is to broadcast these transactions on the peripheral logic bus so that the
processor core can snoop the L1 cache as needed (if snooping is enabled). Table 5-5 shows
all the types of transactions reflected by the CCU to the processor core for snooping.
stwcx., reservation set
CCU takes no further action.
(The MPC8240 does not support atomic
references in PCI memory space.)
tlbsync
CCU takes no further action.
Graphic write (ecowx)
Processor transaction error. Machine check
signalled to processor core (if enabled)
Graphic read (eciwx)
Processor transaction error. Machine check
signalled to processor core (if enabled)
Table 5-6. Transactions Reflected to the Processor for Snooping
Snooped Transaction
Condition Detected by CCU
Processor Response
Read
Non-locked PCI read from memory
All burst reads observed on the bus are
snooped as if they were writes, causing the
addressed cache block to be flushed. A read
marked as global causes the following
responses:
• If the addressed block in the cache is invalid,
the processor takes no action.
• If the addressed block in the cache is in the
exclusive state, the block is invalidated.
• If the addressed block in the cache is in the
modified state, the block is flushed to memory
and the block is invalidated.
Read-with-intent-to-mo
dify (RWITM)-atomic
Locked PCI read from memory
A RWITM operation is issued to acquire
exclusive use of a memory location for the
purpose of modifying it.
• If the addressed block is invalid, the
processor takes no action.
• If the addressed block in the cache is in the
exclusive state, the processor changes the
state of the cache block to invalid.
• If the addressed block in the cache is in the
modified state, the block is flushed to memory
and the block is invalidated.
Table 5-5. CCU Responses to Processor Transactions (Continued)
Processor Transaction
CCU Response
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 ...