The ZipCPU RTL directory contains the two primary wrappers for the ZipCPU: zipbones and zipsystem. These wrappers connect an external wishbone slave interface to the debugging port of the CPU, so that the CPU can be reset, started, stopped, and in general debugged.

The ZipBones would be the appropriate wrapper if you want the CPU to fit in the tightest space possible (Ex: Digilent's CMod S6).

Use the ZipSystem if you want to give the CPU some basic peripherals, such as:

• 2x Interrupt controllers
• Timers, and an experimental timer called zipjiffies that's been with the CPU for some time
• Performance counters, to measure your performance
• A Direct Memory Access Controller

If you are just looking for the CPU's code itself, check out zipcpu.v within the cores subdirectory. That's of the main core of the ZipCPU itself.