hdl

During the work on merging #1419 I figured out that the basic BUFGMUX example works differently on Arty Board and Nexys Video.

The example uses three LEDs:

• led[2] - blinks with slow frequency
• led[1] - blinks with high frequency
• led[0] - blinks with the same frequency as led[2] or led[1] depending on sw[0] state.

On the Arty Board, the example works as intended. On Nexys Video, when

https://github.com/SymbiFlow/sv-tests/blob/8b14f75bc1c3d15d6a5a2ba217800e242f4f5f3e/.github/workflows/sv-tests-ci.yml#L30-L32

https://github.com/SymbiFlow/actions/tree/main/checks

Together with issue #4, we should write a few tests for making sure refdeses do stay consistent. Something like a copy of servo_micro, and a ton of patches on top of it (all parented to one servo_micro, not on a chain, more like a star). Apply each of those patches then see if refdeses are sticking.

git checkout c718fbc~1 examples/servo_micro.py from google/pcbdl@ba3