A schematic design defines the functionality of a logic circuit using one or more schematic files, each of which contains components from a Xilinx-supplied library, such as gates, flip-flops and building-block functions similar to 74xx TTL devices. Schematics can also contain "custom" symbols for which you define the functionality using behavioral modules (similar to PAL devices). Behavioral modules are discussed fully in Chapter 2. The following figure summarizes the design flow.
Figure 1.1 Basic Schematic Design Flow |  |
Currently, the Viewlogic, Mentor and Cadence software packages are directly supported by Xilinx CPLD library and interface for CPLD design entry and simulation. Xilinx also provides the Foundation development system. Other compatible interfaces and CPLD libraries may be available from their manufacturers.
