The Y diagram depicts the different perspectives in the hardware design. Mostly, it is used for the development of integrated circuit

Integrated circuit

An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...

s. Daniel Gajski

Daniel Gajski

Daniel Gajski is a Professor of the School of Information and Computer Science and the School of Engineering at University of California, Irvine, USA...

 and Robert Kuhn

Robert Kuhn

Robert Kuhn may refer to:*Robert Lawrence Kuhn , American author, investment banker, China specialist, television host*Robert T. Kuhn , American clergyman, president of the Lutheran Church - Missouri Synod...

 developed it in 1983. In 1985, Robert Walker and Donald Thomas refined it.

According to this model, the development of hardware is perceived within three domains that are depicted as three axis and produce a Y. Along these axis, the abstraction levels that describe the degree of abstraction. The outer shells are generalisations, the inner ones refinements of the same subject.

The issue in hardware development is most often a top-down design problem. This is perceived by the three domains of behaviour, structure, and the layout that goes top-down to more detailed abstraction levels. The designer can select one of the perspectives and then switch from one view to another. Generally, the design process is not following a specific sequence in this diagram.

• On the system level, basic properties of an electronic system are determined. For the behavioural description, block diagram
  Block diagram
  Block diagram is a diagram of a system, in which the principal parts or functions are represented by blocks connected by lines, that show the relationships of the blocks....
  
  s are used by making abstractions of signals and their time response. Blocks used in the structure domain are CPU
  Central processing unit
  The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
  
  s, memory chip
  Computer memory
  In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
  
  , etc.
• The algorithmic level is defined by the definition of concurrent algorithms (signals, loops, variables, assignments). In the structural domain, blocks like ALU
  Arithmetic logic unit
  In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...
  
  s are in use.
• The Register-Transfer Level
  Register Transfer Language
  In computer science, register transfer language is a term used to describe a kind of intermediate representation that is very close to assembly language, such as that which is used in a compiler. Academic papers and textbooks also often use a form of RTL as an architecture-neutral assembly language...
  
  (RTL) is a more detailed abstraction level on which the behaviour between communicating registers and logic units is described. Here, data structures and data flows are defined. In the geometric view, the design step of the floorplan is located.
• The logical level is described in the behaviour perspective by boolean equations. In the structural view, this is displayed with gates and flip-flops
  Flip-flop (electronics)
  In electronics, a flip-flop or latch is a circuit that has two stable states and can be used to store state information. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic...
  
  . In the geometric domain, the logical level is described by standard cell
  Standard cell
  In semiconductor design, standard cell methodology is a method of designing application-specific integrated circuits with mostly digital-logic features. Standard cell methodology is an example of design abstraction, whereby a low-level very-large-scale integration layout is encapsulated into an...
  
  s.
• The behaviour of the circuit level is described by mathematics using differential equation
  Differential equation
  A differential equation is a mathematical equation for an unknown function of one or several variables that relates the values of the function itself and its derivatives of various orders...
  
  s or logical equation
  Canonical form (Boolean algebra)
  In Boolean algebra, any Boolean function can be expressed in a canonical form using the dual concepts of minterms and maxterms. Minterms are called products because they are the logical AND of a set of variables, and maxterms are called sums because they are the logical OR of a set of variables In...
  
  s. This corresponds to transistor
  Transistor
  A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
  
  s and capacitor
  Capacitor
  A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
  
  s up to crystal lattices.