106 lines
3.9 KiB
NASM
106 lines
3.9 KiB
NASM
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interrupts segment at 0h ; This is where the disk interrupt
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org 13h*4 ; holds the address of its service routine
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disk_int label dword
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interrupts ends
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screen segment at 0B000h ; A dummy segment to use as the Extra
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screen ends ; Segment so we can write to the display
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code_seg segment
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assume cs:code_seg
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org 0100h ; ORG = 100h to make this a .COM file
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first: jmp load_watch ; First time through jump to initialize routine
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msg_part_1 db 'Disk error: ' ; Here are the error messages
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msg_part_2 db 'No response Failed Seek NEC Error '
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db 'Bad CRC SeenDMA Overrun Impos Sector'
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db 'No Addr MarkW. ProtectedErr Unknown '
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first_position dw ? ; Position of 1st char on screen
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flags dw ?
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screen_seg_offset dw 0 ; 0 for mono, 8000h for graphics
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old_disk_int dd ? ; Location of old disk interrupt
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ret_addr label dword ; Used in fooling around with
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ret_addr_word dw 2 dup(?) ; the stack
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disk_watch proc far ; The disk interrupt will now come here
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assume cs:code_seg
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pushf ; First, call old disk interrupt
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call old_disk_int
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pushf ; Save the flags in memory location "FLAGS"
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pop flags ; (cunning name)
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jc error ; If there was an error, carry flag will have
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jmp fin ; been set by Disk Interrupt
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error: push ax ; AH has the status of the error
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push cx ; Push all used registers for politeness
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push dx
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push di
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push si
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push es
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lea si,msg_part_1 ; Always print "Disk Error: " part.
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assume es:screen ; Use screen as extra segment
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mov dx,screen
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mov es,dx
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mov di,screen_seg_offset ; DI will be pointer to screen position
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add di,first_position ; Add to point to desired area on screen
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call write_to_screen ; This writes 12 chars from [SI] to [DI]
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mov dx,80h ; Initialize for later comparisons
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mov cx,7 ; Loop seven times
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e_loop: cmp ah,dh ; Are error code and DH the same?
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je e_found ; If yes, Error has been found
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add si,12 ; Point to next error message
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shr dh,1 ; Divide DH by 2
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loop e_loop ; Keep going until matched DH = 0
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cmp ah,3 ; Error code no even number; 3 perhaps?
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je e_found ; If yes, have found the error
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add si,12 ; Err unknown; unknown error returned
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e_found:call write_to_screen ; Write the error message to the screen
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pop es ; Restore the registers
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pop si
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pop di
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pop dx
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pop cx
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pop ax
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fin: pop ret_addr_word ; Fooling with the stack. We want to
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pop ret_addr_word[2] ; preserve the flags but the old flags
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add sp,2 ; are still on the stack. First remove
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push flags ; return address, then flags. Fill flags
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popf ; from "FLAGS", return to correct addr.
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jmp ret_addr
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disk_watch endp
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write_to_screen proc near ; Puts 12 characters on screen
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mov cx,12 ; Loop 12 times
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w_loop: movs es:byte ptr[di],cs:[si] ; Move to the screen
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mov al,7 ; Move screen attribute into screen buffer
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mov es:[di],al
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inc di ; Point to next byte in screen buffer
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loop w_loop ; Keep going until done
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ret
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write_to_screen endp
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load_watch proc near ; This procedure initializes everything
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assume ds:interrupts ; The data segment will be the interrupt area
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mov ax,interrupts
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mov ds,ax
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mov ax,disk_int ; Get the old interrupt service routine
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mov old_disk_int,ax ; address and put it into our location
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mov ax,disk_int[2] ; OLD_DISK_INT so we can call it.
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mov old_disk_int[2],ax
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mov disk_int,offset disk_watch ; Now load the address of DskWatch
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mov disk_int[2],cs ; routine into the disk interrupt
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mov ah,15 ; Ask for service 15 of INT 10h
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int 10h ; This tells us how display is set up
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sub ah,25 ; Move to twenty five places before edge
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shl ah,1 ; Mult. by two (char & attribute bytes)
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mov byte ptr first_position,ah ; Set screen cursor
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test al,4 ; Is it a monochrome display?
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jnz exit ; Yes - jump out
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mov screen_seg_offset,8000h ; No, set up for graphics display
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exit: mov dx,offset load_watch ; Set up everything but this program to
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int 27h ; stay and attach itself to DOS
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load_watch endp
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code_seg ends
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end first ; END "FIRST" so 8088 will go to FIRST first.
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