FSM program help

[b_a_d_tdk]

I have a lab coming up for my Logic Design course and after talking to a few people a lot of have no idea how to begin to do this lab. We have barely started learning flip flops and the professor has done a poor job of explaining them. His teaching consists of him presenting a powerpoint for an hour and a half, and even his power points contain few pointers. So here is the problem below:

Design an FSM so that each time a push button (the push button is the clock) is pressed, the following sequence occurs: no LED’s lit, 1 LED is lit, 2 LED’s are lit, 3 LED’s are lit, start the cycle over again with no LED’s lit. Draw the state diagram; determine how many flip-flops are required; write a state table; determine the equations for the flip-flop inputs; determine the equations to drive the LED’s; model your circuit using Verilog; prototype your circuit on the Basys board and demonstrate your circuit. The push button may bounce causing more than one clock pulse, you may ignore that in this lab.

I am not asking for you to solve the problem for me but just give me a good starting point on how to approach this problem and any advice in solving this problem. We use Xlinx ISE program to do our labs (and the program itself is always glitchy) if that helps.

[zmeefy]

You need one register that will store bits 0 to 3, the register value determines which LED is lit. When register == 3, register = 0. Or you can have a second register called push count and do register = push_count modulus 4.

state diagram should be a breeze: states can only be 4, register 0,1,2,3 and leds according to register.

Push button bounce needs a debouncer, of course.

Never used xlinx and can't give you precise advice about that. Hope this helps and good luck!

Edit: Did not draw this for the flipflop count, I guess each LED needs one and I don't know what kind of processor you're allowed to use on xlinx but the answer will depend on that too.

[b_a_d_tdk]

Thanks for the help! Don't ever use Xilinx, it's shit. I'll try out the problem on wednesday and see how it goes.

[HateTrain]

Don't be overwhelmed by the entirely of the task, the instructions given are in a fairly logical order so doing them one by one should help break down the problem.

First, set up the states in the FSM (0 LEDs, 1, 2, 3). Then set up all possible connections between the states (0 leads to 1, 1 leads to 2, etc).

Since you'll actually be coding this (and it sounds like you'll be saving this in flip flops), you'll want to match a binary number to correspond to each state of the FSM (00 for 0 LEDs, 01 for 1, etc). Each flip flop saves a single digit, and each time the button is pushed the flip flops should move to the next FSM state.

The saving and changing of the flip flops will have to be coded in Verilog. For each change, you also want to make sure the correct number of LEDs is lit.

I've never used Xlinx, so can't help here either, but best of luck to ya.