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add comment about location that may be modified by sys (and some whitespace changes due to editor)

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git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@1493 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Kenneth J Davis 2009-07-30 03:26:13 +00:00
parent 38abeed649
commit 66c9f421ac
1 changed files with 17 additions and 14 deletions
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31
boot/boot.asm
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@ -398,9 +398,11 @@ read_next:
; check for LBA support ; check for LBA support
mov ah,041h ; mov ah,041h ;
mov bx,055aah ; mov bx,055aah ;
mov dl, [drive] mov dl, [drive]
; NOTE: sys must be updated if location changes!!!
test dl,dl ; don't use LBA addressing on A: test dl,dl ; don't use LBA addressing on A:
jz read_normal_BIOS ; might be a (buggy) jz read_normal_BIOS ; might be a (buggy)
; CDROM-BOOT floppy emulation ; CDROM-BOOT floppy emulation
@ -419,7 +421,7 @@ read_next:
lea si,[LBA_PACKET] lea si,[LBA_PACKET]
; setup LBA disk block ; setup LBA disk block
mov LBA_SECTOR_32,bx ; bx is 0 if extended 13h mode supported mov LBA_SECTOR_32,bx ; bx is 0 if extended 13h mode supported
mov LBA_SECTOR_48,bx mov LBA_SECTOR_48,bx
mov ah,042h mov ah,042h
@ -514,25 +516,26 @@ PrintLowNibble: ; Prints low nibble of AL, AX is destroyed
and AL, 0Fh ; ignore upper nibble and AL, 0Fh ; ignore upper nibble
cmp AL, 09h ; if greater than 9, then don't base on '0', base on 'A' cmp AL, 09h ; if greater than 9, then don't base on '0', base on 'A'
jbe .printme jbe .printme
add AL, 7 ; convert to character A-F add AL, 7 ; convert to character A-F
.printme: .printme:
add AL, '0' ; convert to character 0-9 add AL, '0' ; convert to character 0-9
mov AH,0x0E ; show character mov AH,0x0E ; show character
int 0x10 ; via "TTY" mode int 0x10 ; via "TTY" mode
retn retn
PrintAL: ; Prints AL, AX is preserved PrintAL: ; Prints AL, AX is preserved
push AX ; store value so we can process a nibble at a time push AX ; store value so we can process a nibble at a time
shr AL, 4 ; move upper nibble into lower nibble shr AL, 4 ; move upper nibble into lower nibble
call PrintLowNibble call PrintLowNibble
pop AX ; restore for other nibble pop AX ; restore for other nibble
push AX ; but save so we can restore original AX push AX ; but save so we can restore original AX
call PrintLowNibble call PrintLowNibble
pop AX ; restore for other nibble pop AX ; restore for other nibble
retn retn
PrintNumber: ; Prints (in Hex) value in AX, AX is preserved PrintNumber: ; Prints (in Hex) value in AX, AX is preserved
xchg AH, AL ; high byte 1st xchg AH, AL ; high byte 1st
call PrintAL call PrintAL
xchg AH, AL ; now low byte xchg AH, AL ; now low byte
call PrintAL call PrintAL
retn retn
%endif %endif