Chapter 6 - Programming FPGA Applications in VHDL

Abstract

Through examples, the chapter highlights the control that users can exercise in very high-speed integrated circuit hardware description language (VHDL) to direct proper synthesis of hardware. It discusses how VHDL can be used to describe a design structurally as a composition of subcircuits. It shows how to express hardware in register transfer level (RTL) form. It illustrates how hardware can be generated parametrically in a programmable manner. It outlines the basic tool and workflow for developing VHDL designs. VHDL is one popular programming language that supports RTL hardware descriptions. VHDL enjoys widespread popularity among designers in the industry and with its close cousin, Verilog. Verilog differs from VHDL primarily in the syntax it uses (VHDL is derived from Ada; Verilog, from C), but both languages are periodically reviewed to reflect changing industry realities and expectations. VHDL is a strongly typed, Ada-based programming language that includes special constructs and semantics for describing concurrency at the hardware level. These concurrency constructs are new for most programmers and can be a source of confusion for beginners. Programming in VHDL is quite different from programming in C because of its concurrent semantics. However, it does have several similarities with object-oriented languages like C++ and Java.