FPGA Computer

The Wishbone Bus

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It would be really nice to create a simple design and see it run on the FPGA. The simplest design I can think of is a NOT gate. While the Logi-Pi has built-in button inputs and LED outputs that could be used to test this, I'd also like to utilize the Wishbone bus to facilitate communication between the Raspberry Pi and a design on the FPGA.

The general design, then, is going to be a Wishbone bus with two registers, one for input and one for output. The NOT gate will take input from bit 0 of the input register, negate it, and output to bit 0 of the output register. A Python program on the Raspberry Pi will manipulate bit 0 of the input register and check the output register to see if the design is working.

This breaks down into three general steps: