how to read from bootsecotr ??

[muupp]

hi,iwant ot read first 512 byte from my hard disk partitions
i have to use ax=7305,cx=0ffffh,int 21h
AX = 7305h
CX = FFFFh
DL = drive number (00h=default, 01h=A:, etc.)
SI = read/write mode flags
DS:BX -> disk I/O packet

how can i determine sector and track like this :

AH = 02h
AL = number of sectors to read
CH = low eight bits of cylinder number
CL = sector number 1-63 (bits 0-5)
high two bits of cylinder (bits 6-7, hard disk only)
DH = head number
DL = drive number (bit 7 set for hard disk)
ES:BX -> data buffer

thanks