Cirrus Logic EP93xx - Manual (Page 121)

DS785UM1 4-3
Copyright 2007 Cirrus Logic
Boot ROM
EP93xx User’s Guide
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8. If it is not a Serial Download, attempt to read from SPI Serial Flash (see Figure 4-1 ), and
then follow Steps A, B, C, and D.
A. Check if the first 4 bytes from the Serial Flash are equal to “CRUS” or to “SURC” in
ASCII, verifying the HeaderID
B. Read the next 2048 (decimal count) bytes into the Internal Boot Buffer
C. Turn on Green LED
D. Jump to the start of the Internal Boot Buffer
9. Attempt to read the “CRUS” or “SURC” HeaderID in ASCII in FLASH memory at FLASH
Base + 0x0000, and verify the HeaderID. This is read in for each FLASH Chip select
(see
Figure 4-1 ), and then follow Steps A and B.
A. Turn on Green LED
B. Jump to the start of FLASH memory plus four bytes
10.Attempt to read the “CRUS” or “SURC” HeaderID in ASCII in FLASH memory at FLASH
Base + 0x1000, and verify the HeaderID. This is read in for each FLASH Chip select
(see
Figure 4-1 ), and then follow Steps A and B.
A. Turn on Green LED
B. Jump to the start of FLASH memory
11.Attempt to read the “CRUS” or “SURC” HeaderID in ASCII in memory at 0xC000_0000
and 0xF000_0000, and verify the HeaderID. This is read in for SDRAM or SyncFLASH
boot (see
Figure 4-1 ), and then follow Steps A and B.
A. Turn on Green LED
B. Jump to memory location 0xC000_0004 or 0xF000_0004
12.Attempt to read the “CRUS” or “SURC” HeaderID in ASCII in memory at 0xC000_1000
and 0xF000_1000, and verify the HeaderID. This is read in for SDRAM or SyncFLASH
boot (see
Figure 4-1 ), and then follow Steps A and B.
A. Turn on Green LED
B. Jump to memory location 0xC000_0000 or 0xF000_0000
13.If “CRUS” or “SURC” HeaderID is not found, copy dummy vectors into low SDRAM, and
then follow Step A.
A. Flash Green LED
4.1.2.3 Flowchart
Figure 4-1 provides a flow chart for operation of the Boot ROM software.