L2 Instruction Cache
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
11-17
11.4.6.7 Fetch Operation
Fetch is an operation in which data is read from higher level memory and written to the cache
memory. A miss access initiates the fetch operation. When the transferred data is not located in
the same burst of the data which is required by the miss access, the operation is called a prefetch
(this is a predictive fetch). If a fetch operation is required, and the appropriate cache memory
location is full, a thrash operation is executed. This operation frees cache memory locations for
the use of the required fetch of recent miss access.
Basic fetch sequence is as follows:
A miss access invokes a fetch operation.
A cache line is allocated and invalidated.
Once the missed VBR is fetched, the initiator releases the fetch unit. Fetch and prefetch
operations continue according to the fetch unit configuration.
11.4.7 Debug Mode
Cache debug mode is a special state that allows observation and control over the cache internal
state. It allows access to the PLRU bits, TAG and VALID bits, and ICache memory.
Note:
You can only invoke the L2 ICache debug mode when all the DSP core subsystems
and all the L1 ICaches inside the DSP core subsystems are in the debug state.
The L2 ICache debug mode is initiated by setting a dedicated bit in the cache control registers.
The L2 ICache state registers are accessible through the internal MBus when the cache debug
mode bit is set. Any attempt to invoke the cache debug mode while a sweep operation is ongoing
is ignored and discarded. In addition, you should only invoke the debug mode while the cache is
idle. Use the following steps to invoke the L2 ICache debug mode:
1.
Place all DSP core subsystems into debug mode.
2.
Place all L1 ICaches in all DSP core subsystems into debug mode.
3.
Verify that four DSP core subsystems are in debug mode by checking the core debug
status bits in the General Status Register 1 (GSR1[CORE_DEBUG_STS]). All bits
should be set to 1. See Chapter 8, General Configuration Registers for details.
4.
Make sure that no accesses (read or write) are made to the L2 ICache and verify that the
ICache is idle by checking the L2 ICache idle bit in GSR1 (GSR1[L2I_IDLE]).
5.
Place the L2 ICache into debug mode by writing a 0b1 to L2IC_CR2[CDM].
You must make sure that the DSP core subsystems are all in the debug state before exiting the
cache debug mode. Do not clear the Debug mode bit directly by setting the ECR[EX] bit to force
the DSP core subsystem into its execution state.
Use the following steps to exit the L2 ICache debug mode:
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...