Loading The Preloader Image - Altera cyclone V Technical Reference

A-32

Loading the Preloader Image

Table A-18: Shared Memory Locations
Shared Memory Content
Version Number
Register
stat
Loading the Preloader Image
The boot ROM code loads the image from flash memory into the on-chip RAM and passes control to the
preloader. The boot ROM code checks for a valid image by verifying the header and cyclic redundancy
check (CRC) in the preloader image.
The boot ROM code checks the header for the following information:
• Validation word—validates the preloader image. The validation word has a fixed value of 0x31305341.
• Version—indicates the header version.
• Program length—the total length of the image (in 32-bit words) from offset 0x0 to the end of code area,
including exception vectors and CRC.
• Checksum—a checksum of all the bytes in the header, from offset 0x40 to 0x49.
The preloader image has a maximum size of 60 KB. This size is limited by the on-chip RAM size of 64 KB,
where 4 KB is reserved as a workspace for the boot ROM data and stack. The preloader can use this 4 KB
region (for its stack and data, for example) after the boot ROM code passes control to the preloader. This
4 KB region is overwritten by the boot ROM code on a subsequent reset. The following figure shows the
preloader image layout in the on-chip RAM after being loaded from the boot ROM.
Figure A-13: Preloader Image Layout
0xFFFFFFFF
0xFFFFF000
0xFFFF0050
0xFFFF004C
0xFFFF0040
0xFFFF0000
Altera Corporation
Address Location
+ 0x0008
r0
+ 0x0038
r0
Reserved at Reset
Spare/Unused
CRC
User-Defined Code
Entry Point
Header
Exception Vectors
Description
The register value in shared memory is
stat
only valid if the value of this shared
memory location is 0x00000000.
This location holds the last value the boot
ROM writes to the
stat
Reset Manager before it is erased.
Checksum
Spare (0x0000)
Program Length
Flags
Version
Validation Word
cv_5v4
2016.10.28
register in the
0x4C
0x4A
0x48
0x46
0x45
0x44
0x40
Booting and Configuration
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