Custom Logic
Quite literally, custom logic is logic (or intelligence) that you create yourself and add in to your design. You would typically add your own custom logic into a design where the functionality required cannot be implemented using the FPGA-ready components shipped with Altium Designer.
In Altium Designer, custom logic is implemented using a hierarchical design approach, and using any combination of generic logic components, C or HDL code (VHDL or Verilog). In addition, provision of a Custom Wishbone Interface component allows you to quickly hook your custom logic into your existing bus-based system – creating your own Custom Wishbone Peripheral – without needing any knowledge of the workings of that bus system.
Figure 1. Adding custom logic through creation of hierarchical FPGA designs.
Vendor-specific FPGA primitives can also be used to provide the desired functionality, but use of such devices limits the portability of the design – locking it into a specific device family or, in some cases, specific physical FPGA device.