Verification of Parameterised FPGA Circuit Descriptions with Layout ...

CHAPTER 2. BACKGROUND AND RELATED WORK 15
block addthree ((wire a, wire b), wire c) ∼ (wire d) {
wire t.
(a,b) ; add ; t.
(c, t) ; add ; d.
}
2.3 Quartz
Figure 2.3: A Quartz block which adds together three numbers
Quartz [62, 65] is a declarative block composition language intended for describing digital
circuits. A Quartz description is composed of a series of blocks which are defined by their
name, interface type, local definitions and body statements. A block’s interface is divided,
in a relational style, into a domain and a range. Primitive blocks represent hardware or
simulation primitives and control the function of the circuit, while composite blocks control
the structure and inter-connections of the primitives.
Blocks can be visualised geometrically, typically as four-sided tiles that can be placed on a
two dimensional surface in some inter-connected manner. An abstract additional dimension
allows for the connection of additional signals such as a clock or static parameter values
without disturbing the underlying geometry. Figure 2.3 illustrates the Quartz description and
visual representation for a block which adds together three values, the dotted line indicates
the division between the block’s domain and range. It is common to reason about and
refine Quartz and Ruby designs using pictures and tools have been developed for Ruby to
produce design diagrams automatically [25]. This pictorial interpretation is a useful aid to
implementation, since interconnection is often minimised by careful placement of components.
Quartz differs from existing relational and functional languages by allowing designers to
mix VHDL-like and relational styles in a single design as appropriate. The language is a
development of work on Pebble [46] and the Ruby [31] relational calculus.