Cirrus Logic EP73xx - Manual (Page 75)

EP7309/11/12 User’s Manual - DS508UM4 6-1
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Copyright Cirrus Logic, Inc. 2003
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6
Chapter 6
6 Processor 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.
The processor, in either mode, can be configured to interface with a big or little endian
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
• Unique memory map
• Boots from internal Boot ROM
• Waits for input from UART1
External Boot Mode
• Unique memory map
• Boots by fetching instructions from address 0x0