Q: When I use my new release of UTMOST (10.10.1.R) I experience unexpected program exits, especially when trying to access an Attributes screen from an UTMOST Graphics screen. What is the reason for this ? Can it be avoided ?

A: Problems like this can be experienced if the path length to the VYPER installation directory is too long. In the latest release of the VYPER products the path to the VYPER installation directory should be less than 23 characters in length. Appendix B of the SILVACO Installation, Migration and Troubleshooting Guide (March 1995) details some considerations which should be taken into account when choosing the installation directory refered to as <install_dir>. For a VYPER installation an installation directory (<install_dir>) called:

/users/silvaco (14 characters)

would be acceptable but an installation directory called:

/users/john/test/silvaco (24 characters)

may lead to problems during the operation of UTMOST. If the latter <install_dir> path length is reduced by one character then correct UTMOST operation will be assured. See Chapter 4 of the SILVACO Installation, Migration and Troubleshooting guide for more information regarding the Installation directory structure and utilities.

Q: I have difficulty connecting UTMOST to the HSPICETM circuit simulator. I am sure that I am giving the correct directory path to the location of HSPICETM but when I try to run an UTMOST simulation using HSPICETM as an External
Simulator I get the following message in the UTMOST main window:

Can't Run SPICE.

How can I rectify this ?

A: The most common cause of problems with linking UTMOST to HSPICETM in the current release of VYPER seems to be the absence of the include HSPICE file. This file should reside in the


directory and the UTMOST user should have read and write access to this file. If, for some reason, this file is missing and cannot be found elsewhere then it can be created quite simply. The include HSPICE file should contain only six lines of text as shown below:







Further information on the topic of connecting an external circuit simulator to UTMOST can be found in Appendix F of the UTMOST III Extractions Manual, Volume 3, January 1995.

Q: If I try to re-connect an external circuit simulator using the VYPER Net Setup option VYPER

(a) simply will not allow me to do this and exits or

(b) allows the connection but fails to run simulations later.

What can I do in these situations ?

A: The first situation, i.e. (a), can happen if the user does not specifically define a path in the VYPER Configuration Connect screen for the external simulator in question. No problems will be experienced unless the UTMOST user needs to re-connect the external simulator. In this situation VYPER will exit. The solution to this problem is to edit the .vyper.rc file which can be found in the user's vyper_data directory and delete the line where the path to the external simulator is defined. This line will be something like:

#set HSPICE_computername_PATH = ""

Once this is done then the user can proceed with the connection of the external simulator. Explicitly defining the path will ensure that VYPER will not exit in the same manner during future simulator re-connections.

The second situation, i.e. (b) above, can happen if the user has supplied a specific path to the external circuit simulator location. When a re-connection is attempted, VYPER sometimes tries to add an extra backslash "/ " character to the end of the previously defined path (see Figure 1 below). The extra character will be visible in the VYPER Configuration Connect screen should be removed before the Apply button is pressed.

Figure 1. VYPER configuration connect screen showing extra " / " character.