Thats not the problem. That bit is correct, here the piece of the code that gives me the error:

mov a, #_HD_D_HEAD
;Selects master device. LBA on
mov r2, #11100000b
acall HD_Write

acall HD_Busy

mov a, #_HD_D_HEAD
acall HD_Read
mov a, r2
;display tha decimal str correspondent to A
;on the LCD
acall DispNum

;Space betwen numbers
mov a, #' '
acall LcdCmd

; Until this point every thing was all right.
; The Device Head Register reads OK
; But this one for example (Device
; Cylinder Low) doesn´t!
; it read always 0x00, and Device
; Sector Count reads always 0x01
mov a, #_HD_CYL_LO
mov r2, #10000000b
acall HD_Write

acall HD_Busy

mov a, #_HD_CYL_LO
acall HD_Read
mov a, r2
acall DispNum

Gabriel