Élan™SC520 Microcontroller User’s Manual
3-1
CHAPTER
3
SYSTEM INITIALIZATION
3.1
OVERVIEW
This chapter provides information and guidelines for initializing the ÉlanSC520
microcontroller. Several source code examples of information described in this chapter are
available on the AMD web site. This CodeKit software is tested source code for example
applications. To obtain this software, as well as other product information and tools, access
the AMD home page at www.amd.com and follow the Embedded Processors link.
From a software perspective, the types of systems that can be developed with the
ÉlanSC520 microcontroller fall into two broad categories, native embedded systems and
systems that use a BIOS
1
.
Of course, these are not the only types of systems that can be built with the ÉlanSC520
microcontroller. It is quite possible to develop hybrid systems that have a BIOS but do not
run a “desktop” operating system like Windows
®
, DOS, Unix, or Linux. While there are
many possible ways to initialize the ÉlanSC520 microcontroller, any initialization sequence
can be derived from the following two techniques.
■
System initialization with a BIOS
■
System initialization for a native embedded system without a BIOS
For systems with a BIOS, most, or all, of the system initialization is done by the BIOS while
the system is running in real mode. After initialization, the BIOS loads an operating system
or application from nonvolatile media, which is generally a disk drive, but could be Flash
memory or other media. The operating system or application begins operating in real mode
and then may make its own transition into protected mode. Windows
95 and Windows NT
®
are examples of such operating systems. Real-time operating systems can also operate in
this manner.
BIOS initialization can be complex. Some BIOS products may make a temporary transition
into protected mode to perform certain operations and then revert back to real mode, before
passing execution to an operating system or application. Such behavior is dependent on
how the BIOS is written and the features provided and are beyond the scope of this
discussion.
For embedded systems, the initialization sequence is usually much simpler and generally
occurs primarily in protected mode. In this scenario, the processor comes up from a reset
and transitions into protected mode as soon as possible. The only real-mode code in the
system is the code required to jump from the reset vector and the execute code that causes
the ÉlanSC520 microcontroller to transition into protected mode.
3.1.1
Native Embedded Initialization Sequence
Many systems designed with the ÉlanSC520 microcontroller are native embedded systems
that do not have a BIOS. The software architecture for such systems can take many forms.
1. A BIOS is a PC software component. It is a set of real-mode code that is responsible for
initializing the system and providing a standard set of I/O and system services used by an
operating system and application level software. These services are provided via a standard
interface.
Содержание Elan SC520
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Страница 28: ...Introduction xxviii lan SC520 Microcontroller User s Manual...
Страница 42: ...Architectural Overview 1 14 lan SC520 Microcontroller User s Manual...
Страница 78: ...System Initialization 3 22 lan SC520 Microcontroller User s Manual...
Страница 108: ...Clock Generation and Control 5 10 lan SC520 Microcontroller User s Manual...
Страница 118: ...Reset Generation 6 10 lan SC520 Microcontroller User s Manual...
Страница 148: ...System Arbitration 8 24 lan SC520 Microcontroller User s Manual...
Страница 214: ...SDRAM Controller 10 36 lan SC520 Microcontroller User s Manual...
Страница 230: ...Write Buffer and Read Buffer 11 16 lan SC520 Microcontroller User s Manual...
Страница 288: ...GP Bus DMA Controller 14 22 lan SC520 Microcontroller User s Manual...
Страница 316: ...Programmable Interval Timer 16 8 lan SC520 Microcontroller User s Manual...
Страница 328: ...Software Timer 18 4 lan SC520 Microcontroller User s Manual...
Страница 346: ...Real Time Clock 20 12 lan SC520 Microcontroller User s Manual...
Страница 360: ...UART Serial Ports 21 14 lan SC520 Microcontroller User s Manual...
Страница 414: ...AMDebug Technology 26 8 lan SC520 Microcontroller User s Manual...