F 100 FFFF 0

a
org 400
; Tests PRIMARY Master Disk Drive (P0) using Registers: 1Fxh/3F6h
mov     dx,3F6  ; Alternate status register.
in      al,dx
and     al,80
jnz     403     ; Read until not busy.
mov     dx,1F7  ; Command register.
mov     al,90   
out     dx,al   ; Execute Device Diagnostic.
mov     dx,3F6
in      al,dx
and     al,80
jnz     411     ; Wait until not busy.
mov     dx,1F1  ; Error register
in      al,dx
and     al,1    ;   Device 0 passed?
jz      453     ; If 'No' -> exit
mov     dx,3F6  ; Alternate status register.
in      al,dx
and     al,80
jnz     421     ; Read until not busy.
mov     dx,1F6  ; Device/Head register.
mov     al,E0   ;   Select Device 0.         <-- Primary MASTER drive.
out     dx,al   ; Write Device register.
mov     dx,3F6  ; Alternate status register.
in      al,dx
and     al,80
jnz     42F     ; Wait until not busy.
in      al,dx
and     al,40
jz      434     ; Wait until data ready.
mov     dx,1F7  ; Command register.
mov     al,EC   ;   ATA Identify Device Command.
out     dx,al   ; Write command.
mov     dx,3F6  ; Alternate status register.
in      al,dx
and     al,80
jnz     442     ; Wait until not busy.
mov     dx,1F0  ; Data register.
mov     di,100  ; Address of data buffer (could be located elsewhere)
mov     cx,100  ; 256 words of data.
cld
rep             ; REP INSW
db      6d      
int     3


g =400

d 100 2ff

q