I searched for NIM forum H-bridge and found a couple of posts. Perhaps you can borrow some H-bridge schematics for use in your project.

is H-bridge is located in logic?

because most of the stuff in subPLD files are logic

also, does the stepper motor consider synchronous or asynchronous?

(1) Well, H-bridge uses components such as power MOSFETs and other logic gates. Perhaps you can check out the guys in the NIM forum playing with H-bridges. I have been playing with Circuit Lab and LT-Spice from circuit design and simulation. But I don't find simulation very useful. I usually use real components and proto boards and test the real hardware. Perhaps I can find some Ctt Lab' H-Bridge simulation schematics for your reference.

But perhaps your prof can give you the basic schematic with the H-bridge, and you only need to add combinatorial and sequential logic devices to complete the assignment. (2) I think step motor driver is synchronous, otherwise the motor would move out of sync. But I am not very sure.

I search Circuit Lab's simulation schematics and found the following. You can use the link to get the schematic and read it using EESE's built in Cct Lab tool. But I think you cannot copy and paste to the NIM simulator.

circuitlab.com/circuit/y49w33/motor-driver-using-mosfets

But you might not need to touch H-Bridge, because your prof has not taught that yet. So you might need to confirm with your prof, otherwise you might be wasting your time.

Ah, tea time. See you later this evening or tomorrow. Good luck. Cheers.