At the highest level in the design hierarchy the system description is expressed in terms of functional blocks and data paths.This
architecture diagram effectively details the operartions performed on the data and the information flow through the system without specifying how these features are implemented.This part of a design can be regarded as the data
architecture.
The control and timing circuitry associated with a design are normally omitted at this level .This is because their inclusion is implicit in any design and also because such circuitry can be regarded as an implementational detail.