Up and down digital circuit state diagram

[Lucifre]

I need to design a digital circuit, that will have three outputs (three bits), and two push buttons. There are three possible output combinations ( in binary) 001, 010, 100. ( 1, 2, 4 in decimal). Now the two push buttons will be labeled "up" and "down". When Up is pressed the outputs will change to next higher state. For example, when ouptut is at (001) (decimal 1) it will go to 010 ( decimal 2), when output is at 100 ( 4 decimal) and "up" is pressed it will go back to 001. The down button will basically count down, meaning when output is at 100 and "down" button is pressed the output will change to 010. when output is at 001 and "down" is pressed it will go to 100.

Anyone have an idea on how to aproach this problem? I don't need specific circuits, all i need is a word description of solution ( i will design circuit myself).

 

[skal81]

Re: Engineering Problem

It depends what is ur objective. If you want to do that in a FPGA, then write the VHDL code describing this behavior.
If you want to build with discrete logic, u need to find the equation of each output.

Anyhow, here the design approach I would use:

1) Write the state machine
There are 2 inputs and u need to think the different possibilties of actions.
Also write the output corresponding
2) From the state machine
Find the equations for both state machine and output

Remember however that this will give u a working system but not optimized. It's a start point. Then u need to find "tricks" by yourself to improve.
Good luck

 

[neoaspilet11]

Re: Engineering Problem

Here is your state diagram
http://C:\Documents and Settings\jwong\Desktop\UP_DOWN.pdf

The diagram consists of three States. which presumably will be implemented using JK flipflops. you can create you state table from here and create your equations then down to your implementation.

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[tramp]

Re: Engineering Problem

HI,

You have to use three bit serial to parallal left/ight shift register.Left/right direction will be decided by up/down key.Register will be initialised at 001 state.
Combination of up/down keys through capacitor & debounce circuit will be used as clock for shift register.For deciding diection(let say left when '0' & right
when '1'),you have to ues one latch of which reset pin is tied to up button & set pin tied to down button & output is taken as left/right dirction control signal.