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MCF5272 User’s Manual
Instruction Cache Overview
else if (address == ACR1-address including mask)
effective attributes = ACR1 attributes
else effective attributes = CACR default attributes
Addresses matching an ACR can also be write-protected using ACR[WP].
Reset disables the cache and clears all CACR bits. Reset does not automatically invalidate
cache entries; they must be invalidated through software.
The ACRs allow CACR defaults to be overridden. In addition, some instructions (for
example, CPUSHL) and processor core operations perform accesses that have an implicit
caching mode associated with them. The following sections discuss the different caching
accesses and their associated cache modes.
4.5.2.3.1 Cacheable Accesses
If ACRn[CM] or the default field of the CACR indicates the access is cacheable, a read
access is read from the cache if matching data is found. Otherwise, the data is read from
memory and the cache is updated. When a line is being read from memory, the longword
in the line that contains the core-requested data is loaded first and the requested data is
given immediately to the processor, without waiting for the three remaining longwords to
reach the cache.
4.5.2.3.2 Cache-Inhibited Accesses
Memory regions can be designated as cache-inhibited, which is useful for memory
containing targets such as I/O devices and shared data structures in multiprocessing
systems. Do not cache memory-mapped registers (for example, registers shown with an
MBAR offset). If the corresponding ACRn[CM] or CACR[DCM] indicates cache-inhibited
the access is cache-inhibited. The caching operation is identical for both cache-inhibited
modes, which differ only regarding recovery from an external bus error.
In determining whether a memory location is cacheable or cache-inhibited, the CPU checks
memory-control registers using the following priority:
1. RAMBAR
2. ROMBAR
3. ACR0
4. ACR1
5. If an access does not hit in RAMBAR, ROMBAR, or the ACRs, the default is
provided for all accesses in CACR.
Cache-inhibited write accesses bypass the cache and a corresponding external write is
performed. Cache-inhibited reads bypass the cache and are performed on the external bus,
except when all of the following conditions are true:
•
The cache-inhibited fill-buffer bit, CACR[CEIB], is set.
•
The access is an instruction read.
•
The access is normal (that is, TT = 0).
Содержание DigitalDNA ColdFire MCF5272
Страница 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Страница 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Страница 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Страница 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Страница 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Страница 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Страница 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Страница 338: ...13 44 MCF5272 User s Manual Application Examples ...
Страница 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Страница 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Страница 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Страница 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...
Страница 548: ...INDEX Index 12 MCF5272 User s Manual ...