mov ah , 0x02 int 0x13 code example

Example: mov ah , 0x02 int 0x13

.READ:
  mov ax , (loading address)
  mov es , ax
  mov bx , (segment address, maybe?) ; if you load to address 0x8000 then, ax is 0x0800,and bx is 0x00

  mov ah , 0x02 ; read mode
  mov al , (sector count to read)
  mov ch , (cylinder number)
  mov cl , (sector number)
  mov dh , (head number)
  mov dl , (drive number , A=0x00 , C=0x80)
  int 0x13 ; BIOS disk interrupt

  jc .READ ; failed?? jump to .READ
;success!!