Add comments for introducing startup sequence for DUET boot disk.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8043 6f19259b-4bc3-4df7-8a09-765794883524

1 files changed, 15 insertions, 3 deletions

diff --git a/DuetPkg/BootSector/bootsect.S b/DuetPkg/BootSector/bootsect.S
index 62f50aca49..91a1966c9b 100644
--- a/DuetPkg/BootSector/bootsect.S
+++ b/DuetPkg/BootSector/bootsect.S
@@ -9,13 +9,25 @@
 #*   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,                     

 #*   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.             

 #*   

-#*    bootsect.asm

+#*   bootsect.S

 #*  

-#*   Abstract:

+#*   bootsect.S is built as 16-bit binary file in 512 bytes and patched to disk/partition's 

+#*   first section - boot sector. 

+#*

+#*   The startup sequence for DUET disk boot sector is:

+#*

+#*   1, LegacyBios check 0xAA55 signature at boot sectore offset 0x1FE to judget 

+#*      whether disk/partition is bootable.

+#*   2, LegacyBios will load boot sector to 0x7c00 in real mode, pass BPB data and

+#*      hand off control to 0x7c00 code.

+#*   3, boot sector code simply parse FAT format in boot disk and find EfiLdr binary file 

+#*      and EfiVar.bin if exists. For first boot, EfiVar.bin does not exist.

+#*   4, boot sector load the first sector of EfiLdr binary which is start.com to

+#*      0x2000:0x0000 address.

+#*   5, boot sector handoff control to 0x2000:0x0000 for start.com binary.

 #*

 #------------------------------------------------------------------------------

 

-        #.MODEL small

         .stack: 

         .486p: 

         .code16