INT 21 - PCW Weather Card interface - GET DATA SEGMENT
        AX = 7070h
        BX = 6060h
        CX = 7070h
        DX = 7070h
        SX = 7070h
        DX = 7070h
Return: AX = segment of data structure
Notes:  the data structure is at offset 516 from this segment.
        the update byte is at offset 514 from this segment.  Updates are
          once per second while this byte is nonzero and it is decremented
          once per second.  While this byte is 0 updates are once per minute.

Format of data structure:
Offset  Type    Description
 00h    WORD    hour
 02h    WORD    minute
 04h    WORD    second
 06h    WORD    day
 08h    WORD    month
 0Ah    WORD    year
 0Ch    WORD    ???
 0Eh    WORD    relative barometric pressure (in 1/100 inches)
 10h    WORD    ???
 12h    WORD    ???
 14h    WORD    temperature 1 (in 1/10 degrees F)
 16h    WORD    temperature 1 lowest (in 1/10 degrees F)
 18h    WORD    temperature 1 highest (in 1/10 degrees F)
 1Ah    WORD    temperature 2 (in 1/10 degrees F)
 1Ch    WORD    temperature 2 lowest (in 1/10 degrees F)
 1Eh    WORD    temperature 2 highest (in 1/10 degrees F)
 20h    WORD    wind speed (in MPH)
 22h    WORD    average of 60 wind speed samples (in MPH)
 24h    WORD    highest wind speed (in MPH)
 26h    WORD    wind chill factor  (in 1/10 degrees F)
 28h    WORD    lowest wind chill factor (in 1/10 degrees F)
 2Ah    WORD    ???
 2Ch    WORD    wind direction (in degrees)
 2Eh    WORD    accumulated daily rainfall (in 1/10 inches)
 30h    WORD    accumulated annual rainfall (in 1/10 inches)