31-Bit Prime Detector is a hardware prime number detector for Tiny Tapeout 3. It takes in a shifted-in 31-bit number, and will determine whether it is prime or not.
The user input is shifted in through an SPI-like interface into a 31-bit shift-in, parallel-out register (SIPO). From here, the FSM control logic waits for a rising edge on the ready signal. It then proceeds to try and divide the value in the SIPO by all possibly values below it (up to 31'h00010000, as the maximum possible value). If it finds a value that divides evenly, then it will stop and declare the number not prime (done is high, and is_prime is low). If it doesn't divide evenly by any of the numbers, it will declare the number prime (done and is_prime are high).
Not shown in the picture is one additional output, waiting, which displays whether the Prime Number Detector is currently waiting for another number to run.
Lastly, both reset and ready are buffered by registers to synchronize the inputs, and SCLK is debounced internally through sampling with a depth of 4 (i.e. the internal signal will only change to a value if all 4 samples agree).
My testing infrastructure is based on Cocotb testing in Python with Pytest, automated with Makefiles. To run the tests, you will need Cocotb and Pytest installed, as well as either iverilog or verilator (with the tests being set up to use the former currently):
sudo apt install iverilog verilator
pip3 install cocotb pytestYou will also need to have make installed, although that is default on most systems.
To run the tests, navigate to src/tests and run make all. You will get an intuitive display of whether the tests pass or fail, as well as all of the testing outputs and artifacts in src/tests/build