Cirrus-logic EP73xx Uživatelský manuál Strana 75

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EP7309/11/12 Users Manual - DS508UM4 6-1
Copyright Cirrus Logic, Inc. 2003
66
6
Chapter 6
6Processor Support
Introduction
The EP73xx processor has an internal and external boot mode. In each instance, the
processor will fetch from ROM memory, either internal or external ROM respectively.
Theprocessor, in either mode, can be configured tointerfacewitha bigorlittleendian
device.
Features
Internal Boot ROM for bootloader assistance
External BOOT mode for system boot
Big/little endian Configuration
Operational Overview
The EP73xx processor has two boot modes: internal and external. Each mode dictates
the memory map and how the processor will perform. The processor will boot into
either mode by latching values seen on
nMEDCHG pin during power on reset. Based
on the value, the processor will look to the internal BOOT ROM or to an external
ROM (
CS0) and being fetching instructions from there.
Internal Boot Mode Characteristics
•Uniquememorymap
Boots from internal Boot ROM
•WaitsforinputfromUART1
External Boot Mode
•Uniquememorymap
Bootsbyfetchinginstructionsfromaddress0x0
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