Altera Nios Development Board - Manual (Page 30)

1–22 Altera Corporation
Nios Development Board Reference Manual, Stratix Edition September 2004
Configuration Controller Device (EPM7128AE)
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For details on programming configuration data to flash memory, see the
Nios II Flash Programmer User Guide, or refer to the Nios II IDE online
help.
Safe & User Configurations
The configuration controller can manage two separate Stratix device
configurations stored in flash memory. These two configurations are
conventionally referred to as the safe configuration and the user
configuration. Upon reset or when the Reset, Config button (SW10) is
pressed, the configuration controller will attempt to load the Stratix
device with user configuration data. If this process fails (either because
the user-configuration is invalid or not present), the configuration
controller will then load the Stratix device with safe configuration data.
The configuration controller expects user configuration and safe
configuration files to be stored at fixed locations (offsets) in flash memory.
Table 1–7 shows how the configuration controller expects flash memory
contents to be arranged.
1 A Nios II reference design is pre-loaded into the safe-
configuration region of the flash memory. Altera recommends
that users avoid overwriting the safe configuration data.
When SW9 (Safe Config) is pressed, the configuration controller will
ignore the user configuration and always configure the Stratix device
from the safe configuration. This switch allows you to “escape” from the
situation where a valid–but–nonfunctional user configuration is present
in flash memory.
Using Conventional Flash Memory
The Nios development board includes an 8 MByte flash memory device
(U5) as shown in
Table 1–6 on page 1–23 . It is divided into 128
individually-erasable 64K sectors. The factory-programmed design, and
(more importantly) the on-board configuration controller, makes certain
assumptions about what–resides–where in flash memory.