What is this error message telling me?

[jflanigan]

Eugene,

I am getting the following message when I power on my circuit.

LC Confusing Error Message.JPG (16.92 KiB) Viewed 12540 times

The named circuit runs fine in a standalone test so I suspect the problem is how I am using that circuit.

The identified circuit is the following:

component circuit.JPG (32.55 KiB) Viewed 12540 times

which is being referenced by:

ALU Circuit.JPG (29.95 KiB) Viewed 12540 times

Any suggestions for hunting this down?

Regards,
John

[admin]

Hi John,
The problem here is wiring of one of the AND gates on your adder (presumably the selected one).
So to track it down, please click it on the diagram and look at the very bottom of the LC window. It should show you the name and position of the selected gate. So in this case you are looking for &(16, 22). Once you’ve found the gate, unselect it by clicking on the empty space on the diagram and hover mouse over gate’s pins to see which one is x1. It should be the top one. Then you need to tract all wires connected to this pin directly and through input pins of the adder. To select all connected wires click one of them while holding Shift key and entire conductor will be selected. So presumably we are talking about top input pin of the selected AND gate, which is connected to “b” input of the adder, which is connected to “b” input of ALU and some pin of Logical Unit. If this pin is input one then track further to where “b” input of ALU is connected. Continue until you found two output pins connected together.
Hope this works for you, but if you need more help please send me the file and I’ll try to find the problem.
Eugene

[jflanigan]

Thank you Eugene.

I have followed your directions so it looks like I am suffering from a misunderstanding that hopefully you can cure.

Thank you for your time.

Regards,
John

[admin]

You are welcome.
Here what I’ve found.
First I’ve been deleting from Test harness one by one:
- Decoder symbol, try to power up: error.
- 1 Bit Full Adder, try to power up: error.
- Logical Unit, try to power up: error.
- Main, try to power up: NO errors.
Undo all changes. Now I know the erroneous circuit is Main.
Then the message says: “Input pin x1 of Symbol of Gate: And on LogicalCircuit: 1-Bit Full Adder(16, 22) connected to more than one output pin that are not tri state capable.”
So I drilled down to Main and see that there is Adder on it. Drill down to adder. Click And gate to find which one is 16, 22. (BTW this numbers are coordinates of the symbol of the circuit). It turns out it is the one selected on your second picture. So now which pin is x1? To find out unselect the gate and hover mouse over pins. The top one is x1. Now Hold Shift and click wire connected to it. You will see entire conductor which looks good as it only connects one output of the Input pin “b” to inputs of the And(16, 22) and Xor(16, 16).
That means that error somewhere on the circuit that uses the adder. Switch back to Main (BTW Ctrl-Tab will circle you through history of viewed diagrams). Shift-Click wire connected to “b” pin of the adder.
Again it is look good connecting one output of input pin “b” to two inputs. Continue back to Test where we started and Shift-click wire connected to input “b” of Main.

WrongWire.png (9.72 KiB) Viewed 12516 times

Here we go - bad wiring as you’ve connected inputs “b” and “f0” of Main together. As a result outputs of two constants connected to some inputs.
Please let me know if you have any further questions.
Eugene

[jflanigan]

Woo Hoo! An inadvertent solder bridge!

Thanks Eugene! I'll post the correct circuit shortly.

One suggestion: How about making the color of wires different from the color of the components? It would make this type of error stand out and it would be easy to implement.