Introduction

Begin a new simulation To do in PSpice? Data from clipboard Data from file Compare methods

Open/Save simulations

Make a circuit look right

Add graphs

Run a simulation

State variables

Miscellaneous options

Advanced features

Begin a new simulation

What must I do in PSpice?

Before MoHAT can interpret a circuit, it must first be run using Orcad's PSpice. Using the specification of PSPice, enter in the circuit as normal. The only thing that must be added is a .PRINT statement before the .END statement that lists the voltages for all nodes connected to the simulated elements. If any voltages are missing, MoHAT will detect them and copy the required text string into your clipboard so that you may quickly rerun the simulation in PSpice. Currents may also be placed after the .PRINT statement if you wish to graph them within MoHAT. Once these requirements are met, run the PSpice simulation and a .out file will automatically be created in the same folder as your .sim file.

Method #1: Getting data into MoHAT via the clipboard

This method provides the quickest means of getting data from PSpice into MoHAT and is recommended for users with modem connections. With this method, you are limited to .out files smaller than about 150KB in size. For larger files, read the heading below titled "Method #1 vs. Method #2" to help you decide if you should use method #2. At this point you should have a .out file with the same name and located in the same directory as your .sim file. Complete the following steps to begin a simulation.

1. In any text editor, open up the .out file you wish to use in MoHAT.
2. Select, or highlight, all the text, and copy it to the clipboard.
3. In MoHAT, click the New link in the control menu.
4. Once the window appears, click the Paste from PSpice button in the lower left corner.
5. At this point, a security box will appear asking you to authorize shockwave to view the contents of your clipboard. Click OK, and the .out file should appear in the large text box.
6. When text appears in the text box, check to make sure it's the correct file.
   • If it is the correct file, then click the Run Simulation button to begin.
   • If it is not the correct file, go back to step 1, and make sure that you use the right .out file.

Method #2: Getting data into MoHAT directly from a file

This method is the simplest to use because you can browse your hard drive to find any .out file from within the MoHAT window, and it is recommended for users with Internet connections faster than a 56K modem. Complete the following steps to begin a simulation.

1. Click the Browse button located below the MoHAT application.
2. From the window that appears, select the .out file you wish to open, and click Open or OK.
3. Double check the file name, and, if it's correct, press the Transfer .out file button.
4. A small browser window will appear to indicate the status of the transfer. Wait for it to say "Transfer Complete" before continuing. (You may work within MoHAT while the file is uploading)
5. Once the transfer is complete, click the New link in MoHAT's control menu.
6. Once the window appears, click the Load from file button in the lower left corner.
7. When text appears in the text box, check to make sure it's the correct file.
   • If it is the correct file, then click the Run Simulation button to begin.
   • If it is not the correct file, go back to step 1, and make sure that you use the right .out file.

Method #1 vs. Method #2

The most common method to input data into MoHAT is by copying the PSpice .out file to your clipboard, then into MoHAT. The only limitation to this method is that once a .out file reaches about 150KB in size, it may never complete the transfer between your clipboard and MoHAT. It tends to just hang the entire browser until it is manually stopped by the user. Any file over 150KB in data probably has far more input steps than necessary to understand the circuit, so reducing the number of DC/AC steps or decreasing the transient analysis time will produce less data, making for a smaller .out file. If your circuit requires a lot of data, then use method #2 since it can handle data files of up to 1 MB.

Method #2 allows you to browse the hard drive for your file, making for a simpler interface. However, the down side to this method is that it takes much longer to transfer the data, and, on a slow Internet connection, this time latency can be very noticeable. To understand this time difference, you will need to understand how MoHAT is set up. When you go to the MoHAT website, your browser downloads the shockwave file to some cache directory on your hard drive before playing it. This way it runs more quickly because it doesn't have to pass data across the Internet. To protect you from malicious hackers who want to damage your computer, shockwave has built-in security measures preventing shockwave programs from viewing the hard drive of the computer running it. Since a shockwave program can't view the hard drive, MoHAT can't allow users to browse their hard drive for the .out file they wish to run. The only means of importing data into shockwave directly from the local machine is through the clipboard, which is how method #1 works.

MoHAT gets around the shockwave security with method #2 because it uses an HTML form document to retrieve your file. The controls to pick a .out file are part of the HTML page that contains the MoHAT shockwave object. Once you click on the Transfer button, your .out file gets uploaded to the remote server and saved in a special temporary directory. Once the file is uploaded and you click the Load from file button in MoHAT, your .out file is re-transfered from the remote server directly into the MoHAT shockwave application located on your hard drive in your browser cache. So you see, transferring a .out file using method #2 requires the file to be transfered across the Internet twice, which may be fine on some machines, but, across a modem, it may not be worth it.

Unless someone actually finds a way of achieving world peace and harmony, there will always be hackers who want to crash your machine, and there will always be security measures to frustrate the rest of us. So until that day, these are the two best methods for getting data into MoHAT from your local machine.