; Reading the harddisk using ports!
; +-------------------------------+ by qark
;
;
; This took me months to get working but I finally managed it.
;
; This code only works for the 286+ so you must detect for 8088's somewhere
; in your code.
;
; Technical Information on the ports:
; Port Read/Write Misc
; ------ ------------ -------------------------------------------------
; 1f0 r/w data register, the bytes are written/read here
; 1f1 r error register (look these values up yourself)
; 1f2 r/w sector count, how many sectors to read/write
; 1f3 r/w sector number, the actual sector wanted
; 1f4 r/w cylinder low, cylinders is 0-1024
; 1f5 r/w cylinder high, this makes up the rest of the 1024
; 1f6 r/w drive/head
; bit 7 = 1
; bit 6 = 0
; bit 5 = 1
; bit 4 = 0 drive 0 select
; = 1 drive 1 select
; bit 3-0 head select bits
; 1f7 r status register
; bit 7 = 1 controller is executing a command
; bit 6 = 1 drive is ready
; bit 5 = 1 write fault
; bit 4 = 1 seek complete
; bit 3 = 1 sector buffer requires servicing
; bit 2 = 1 disk data read corrected
; bit 1 = 1 index - set to 1 each revolution
; bit 0 = 1 previous command ended in an error
; 1f7 w command register
; commands:
; 50h format track
; 20h read sectors with retry
; 21h read sectors without retry
; 22h read long with retry
; 23h read long without retry
; 30h write sectors with retry
; 31h write sectors without retry
; 32h write long with retry
; 33h write long without retry
;
; Most of these should work on even non-IDE hard disks.
; This code is for reading, the code for writing is the next article.
mov dx,1f6h ;Drive and head port
mov al,0a0h ;Drive 0, head 0
out dx,al
mov dx,1f2h ;Sector count port
mov al,1 ;Read one sector
out dx,al
mov dx,1f3h ;Sector number port
mov al,1 ;Read sector one
out dx,al
mov dx,1f4h ;Cylinder low port
mov al,0 ;Cylinder 0
out dx,al
mov dx,1f5h ;Cylinder high port
mov al,0 ;The rest of the cylinder 0
out dx,al
mov dx,1f7h ;Command port
mov al,20h ;Read with retry.
out dx,al
still_going:
in al,dx
test al,8 ;This means the sector buffer requires
;servicing.
jz still_going ;Don't continue until the sector buffer
;is ready.
mov cx,512/2 ;One sector /2
mov di,offset buffer
mov dx,1f0h ;Data port - data comes in and out of here.
rep insw
; ------
mov ax,201h ;Read using int13h then compare buffers.
mov dx,80h
mov cx,1
mov bx,offset buffer2
int 13h
mov cx,512
mov si,offset buffer
mov di,offset buffer2
repe cmpsb
jne failure
mov ah,9
mov dx,offset readmsg
int 21h
jmp good_exit
failure:
mov ah,9
mov dx,offset failmsg
int 21h
good_exit:
mov ax,4c00h ;Exit the program
int 21h
readmsg db 'The buffers match. Hard disk read using ports.$'
failmsg db 'The buffers do not match.$'
buffer db 512 dup ('V')
buffer2 db 512 dup ('L')
;
; Writing to the hard disk using the ports! by qark
; +---------------------------------------+
;
; The only differences between reading and writing using the ports is
; that 30h is sent to the command register, and instead of INSW you
; OUTSW.
;
mov dx,1f6h ;Drive and head port
mov al,0a0h ;Drive 0, head 0
out dx,al
mov dx,1f2h ;Sector count port
mov al,1 ;Write one sector
out dx,al
mov dx,1f3h ;Sector number port
mov al,1 ;Wrote to sector one
out dx,al
mov dx,1f4h ;Cylinder low port
mov al,0 ;Cylinder 0
out dx,al
mov dx,1f5h ;Cylinder high port
mov al,0 ;The rest of the cylinder 0
out dx,al
mov dx,1f7h ;Command port
mov al,30h ;Write with retry.
out dx,al
oogle:
in al,dx
test al,8 ;Wait for sector buffer ready.
jz oogle
mov cx,512/2 ;One sector /2
mov si,offset buffer
mov dx,1f0h ;Data port - data comes in and out of here.
rep outsw ;Send it.
; ------------
mov ax,201h ;We'll read in sector 1 using
mov bx,offset buffer2 ;int13h and see if we are successful.
mov cx,1
mov dx,80h
int 13h
mov cx,512
mov si,offset buffer
mov di,offset buffer2
repe cmpsb ;Compare the buffers.
jne failure
mov ah,9
mov dx,offset write_msg
int 21h
jmp w_exit
failure:
mov ah,9
mov dx,offset fail
int 21h
w_exit:
mov ax,4c00h ;Exit the program
int 21h
write_msg db 'Sector one written to using the ports, OH NO! there goes XP.$'
fail db 'Writing using ports failed.$'
buffer db 512 dup ('A')
buffer2 db 512 dup ('D')
