INT 15 - CASSETTE - READ DATA
        AH = 02h
        CX = number of bytes to read
        ES:BX -> buffer
Return: CF clear if successful
            DX = number of bytes read
            ES:BX -> byte following last byte read
        CF set on error
        AH = status
            00h successful
            01h CRC error
            02h bad tape signals
            04h no data
            80h invalid command
            86h no cassette present
SeeAlso: AH=03h"CASSETTE"