Int 48 Fn 06  - Ti Professional Pc - Calculate Crc                         [b]

   AH = 06h
   ES:BX -> memory block for which to calculate CRC
   BP = size of block in bytes

Return: DX = CRC for block
   ZF set if DX = 0000h

Note:  if the CRC of a memory block is appended to the block, then the CRC
     of the block plus CRC should equal 0000h

See Also: AH=00h,AH=01h,AH=02h,AH=03h,AH=04h,AH=06h,AH=08h,AH=0Ah,AH=0Bh