Chapter 4. Local Memory
4-1
Chapter 4
Local Memory
This chapter describes the MCF5272 implementation of the ColdFire Version 2 core local
memory specification. It consists of the following sections.
•
Section 4.3, “SRAM Overview,” and Section 4.4, “ROM Overview,” describe the
on-chip static RAM (SRAM) and ROM implementations. These chapters cover
general operations, configuration, and initialization. They also provide information
and examples showing how to minimize power consumption when using the ROM
and SRAM.
•
Section 4.5, “Instruction Cache Overview,” describes the cache implementation,
including organization, configuration, and coherency. It describes cache operations
and how the cache interfaces with other memory structures.
4.1 Interactions between Local Memory Modules
Depending on configuration information, instruction fetches and data read accesses may be
sent simultaneously to the SRAM, ROM, and cache controllers. This approach is required
because the controllers are memory-mapped devices and the hit/miss determination is made
concurrently with the read data access. Power dissipation can be minimized by configuring
the ROM and SRAM base address registers (ROMBAR and RAMBAR) to mask unused
address spaces whenever possible.
If the access address is mapped into the region defined by the SRAM (and this region is not
masked), it provides the data back to the processor and any cache or ROM data is discarded.
If the access address does not hit the SRAM, but is mapped into the region defined by the
ROM (and this region is not masked), the ROM provides the data back to the processor and
any cache data is discarded. Accesses from the SRAM and ROM modules are never cached.
The complete definition of the processor’s local bus priority scheme for read references is
as follows:
if (SRAM “hits”)
SRAM supplies data to the processor
if (ROM “hits”)
ROM supplies data to the processor
else if (cache “hits”)
cache supplies data to the processor
else system memory reference to access data
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 ...