Hello IBIS fans, We discovered a potential problem with the port types when using [External Circuit]s. The "Ports under [Model]s" section of the spec discusses the naming convention of the reserved port names used with [External Model]. | The first letter of the port name designates it as either digital ("D") or | analog ("A"). Reserved ports 1 through 13 listed above are assumed or | implied under the native IBIS [Model] keyword. Later, the "Ports under [External Model]s" section describes the port name rules for [External Circuit]s: | The [External Circuit] keyword allows the user to define any number of ports | and port functions on a circuit. The [Circuit Call] keyword instantiates | [External Circuit]s and connects their ports to specific die nodes (this can | include pads). In this way, the ports of an [External Circuit] declaration | become specific component die nodes. Note that, if reserved digital port | names are used with an [External Circuit], those ports will be connected | automatically as defined in the port list above (under [External Circuit], | reserved analog port names do not retain particular meanings). From these sections of the spec we know how to deal with the ports of [External Model]s, i.e. it is known what their type is, but there is a problem with [External Circuit]s. Other than the usage of the reserved digital port names, there is no way of knowing what the port type is for a user defined port name, because we do not have a mechanism to declare port types in IBIS. Unfortunately the [Node Declaration] keyword doesn't do more than list the die nodes and/or pads, so this keyword would not be useful to find out what the type of a port may be that is connected to it. This is a problem, because some tools need to know the type of a port in order to know how to connect things. Looking into the [External Circuit] to find out the port type may not be as easy as it sounds either if only compiled (or encrypted) models are available. I would like to make two suggestions: 1) If the "first letter rule" was only intended to apply to the reserved port names (to be honest, this is not 100 % clear to me from reading the spec.) we need to write a clarification BIRD to clear this up. 2) If the "first letter rule" doesn't apply to user defined port names, I would propose that we invent a port type declaration mechanism to declare the user defined port types. Any comments or questions are appreciated. Thanks, Arpad ============================================================================= -- This message has been scanned for viruses anddangerous content by MailScanner, and isbelieved to be clean. -------------------------------------------------------------------- |For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org |with the appropriate command message(s) in the body: | | help | subscribe ibis <optional e-mail address, if different> | subscribe ibis-users <optional e-mail address, if different> | unsubscribe ibis <optional e-mail address, if different> | unsubscribe ibis-users <optional e-mail address, if different> | |or e-mail a request to ibis-request@eda-stds.org. | |IBIS reflector archives exist under: | | http://www.eda-stds.org/pub/ibis/email_archive/ Recent | http://www.eda-stds.org/pub/ibis/users_archive/ Recent | http://www.eda-stds.org/pub/ibis/email/ E-mail since 1993Received on Wed, 26 Mar 2008 09:39:13 -0700
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