how do I convert a DBL into 8 individual bytes, and vice versa?

[gmaneske]

Using Labview, I need to convert a DBL number into 8 bytes to serially send to a Motorola HC11, and receive back the 8 bytes and convert it into a DBL number.

[RobertoBozzolo]

Have you tried using the Flatten to string and Unflatten from string functions? You'll find them in the Advanced >> Data manipulation palette.
For a discussion of the data storage and of the flattened format, you'll find useful the Application Note 154, found in the LabVIEW help (search in the help for the Flatten to string function for example).
Roberto