# Confused on how to make a counter does what I need it to do?

Joined Apr 29, 2018
6
Hi guys,
I'm currently trying to make a counter so that, it counts if the gear shift fails 3 times then the logic fail ie red light. gear change is successful when S=G, S=G-1, S=G-1.

For this part, the car has a gearbox that can withstand up to a number of unsuccessful gear changes (N) and it will break if that number is reached. The number N ranges from 1 to 7 and must be set via a combination of three separate inputs: N1, N2, and N3. An N value of 0 is not allowed and the gearbox state is undefined for this case. This means that you will have to set N to be non-zero (1..7) before starting the engine engaging the gearbox. Note: In Logisim, you can combine the 3 inputs for N into a single 3 bit input.

#### dl324

Joined Mar 30, 2015
12,931
Welcome to AAC!

For homework questions, you need to show us your best effort and state where you're having difficulty.

It would be helpful if you posted the complete text of the problem. I have no idea what "S=G, S=G-1, S=G-1" means. What do S and G represent?

It would also be helpful if you told us what you're currently studying in this class so we can guess at how to bound solution space.

Joined Apr 29, 2018
6
Welcome to AAC!

For homework questions, you need to show us your best effort and state where you're having difficulty.

It would be helpful if you posted the complete text of the problem. I have no idea what "S=G, S=G-1, S=G-1" means. What do S and G represent?

It would also be helpful if you told us what you're currently studying in this class so we can guess at how to bound solution space.
Im currently studying logic circuit in my IT class.

For this assignment you are required to implement a simple simulation of a gearbox in a car. The gearbox has two inputs. Input 1 (G) represents the current gear (0-7). Input 2 (S) represents the gear that the driver wants to change/shift to (0-7). The gear change is successful if S = G, or if S = G – 1, or if S = G + 1.Any other value for S outside of this range will result in an unsuccessful gear change. Example 1: The current gear (G) is 2 and the gear we want to change to (S) is 3. In this case the requirement S = G + 1 is met and the gear change is successful. Example 2: The current gear (G) is 2 and the gear we want to change to (S) is 4. In this case S is outside the allowed range and the gear change is unsuccessful. Example 3: The current gear (G) is 0 and the gear we want to change to (S) is 0. In this case the requirement S = G is met and the gear change is successful.

The implementation for this part must use only the three basic logic gates (AND, OR, NOT) with maximum 2 inputs. You are required to implement a circuit where the user (you) can input a value for the current Gear (G) using value (G1, G2, and G3) and a gear to change to (S) using value (S1, S2, and S3) and the circuit decodes the G1, G2, G3 and S1, S2, S3 values using a decoder (see lecture notes) made up of only the permitted logic gates to determine if S = G, or if S = G – 1, or if S = G + 1. The output will be a single LED labelled Successful which is lit if S = G, or if S = G – 1, or if S = G + 1 and is not lit for any other values of S and G.

This is the first part of it, and I have completed the cicuit just not sure what i am suppose to do with part B (the one in my initial post).

#### dl324

Joined Mar 30, 2015
12,931
This is the first part of it, and I have completed the cicuit just not sure what i am suppose to do with part B (the one in my initial post).
Post the work you've done so far and your idea(s) for implementing part B.

• Joined Apr 29, 2018
6
Post the work you've done so far and your idea(s) for implementing part B.
This is what i have so far, sorry for some of the scaling.

#### dl324

Joined Mar 30, 2015
12,931
You need to label the inputs and outputs for each schematic. What do the 3 blocks in do? We need to see their contents.

Joined Apr 29, 2018
6
You need to label the inputs and outputs for each schematic. What do the 3 blocks in do? We need to see their contents.
the 3 input is basically the gear that goes from 0-7

#### dl324

Joined Mar 30, 2015
12,931
the 3 input is basically the gear that goes from 0-7
But there are inputs for S and G, so you need to label everything for the benefit of those who didn't design the circuit and can't even begin to try to understand what it does without the inputs and outputs being labeled.

Joined Apr 29, 2018
6
But there are inputs for S and G, so you need to label everything for the benefit of those who didn't design the circuit and can't even begin to try to understand what it does without the inputs and outputs being labeled.
ahhh, i see. I will go through and label them and re upload the files in that case then

#### dl324

Joined Mar 30, 2015
12,931
ahhh, i see. I will go through and label them and re upload the files in that case then
It would also be helpful if you showed your work (truth tables, Kmaps, etc).