Chapter 4. Local Memory
4-5
ROM Overview
4.3.2.3 Programming RAMBAR for Power Management
Depending on the configuration defined by RAMBAR, instruction fetch accesses can be
sent to the SRAM module, ROM module, and instruction cache simultaneously. If the
access is mapped to the SRAM module, it sources the read data, discarding the instruction
cache access. If the SRAM is used only for data operands, setting RAMBAR[SC,UC]
lowers power dissipation by disabling the SRAM during all instruction fetches.
Additionally, if the SRAM holds only instructions, setting RAMBAR[SD,UD] reduces
power dissipation.
Consider the examples on Table 4-3 of typical RAMBAR settings:
ROMBAR can be configured similarly, as described in Section 4.4.2.2, “Programming
ROMBAR for Power Management.”
4.4 ROM Overview
The ROM modules has the following features:
•
16-Kbyte ROM, organized as 4K x 32 bits
•
Contains data tables for soft HDLC (high-level data link control), DTMF (dual-tone
multiple frequency) detection, and tone generation. (The ROM does not contain
instructions.)
•
The ROM contents are not customizeable
•
Single-cycle access
•
Physically located on ColdFire
core's high-speed local bus
•
Byte, word, longword address capabilities
•
Programmable memory mapping
4.4.1 ROM Operation
The ROM module contains tabular data that the ColdFire core can access in a single cycle.
The ROM can be located on any 16-Kbyte address boundary in the 4-Gbyte address space.
Section 4.1, “Interactions between Local Memory Modules,” describes priorities when a
fetch address hits multiple local memory resources.
Table 4-3. Examples of Typical RAMBAR Settings
Data Contained in SRAM
RAMBAR[7–0]
Instructions only
0x2B
Data only
0x35
Both instructions and data
0x21
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 ...