Arnab, Thanks for your interest in IBIS. Explaining all the details in implementing [External Model] would be difficult to do in a single e-mail. :) An IBIS Cookbook update for version 4.1 will be considered once the 4.0 edition is finalized and issued. The example you cite is actually a differential model, which has additional options not shown in the text of your original message. There are also port mapping and other required keywords in the specification example. Simply put, diffio.spi should be a separate file containing a Berkeley SPICE model of the buffer you would like to analyze. This model should contain a number top-level or externally-accessible subcircuit nodes (the nodes are dependent on the ports required by your Model_type; see pages 95-96 of the IBIS 4.1 specification in PDF for the table explaining which ports are required). These nodes correspond to the power and ground connections for your buffer; the output(s) to "the outside world"; and digital connections between the buffer and a logic core. Depending on Model_type, these "digital" connections might include a buffer enable, an input to toggle the buffer and/or an output from the buffer. As SPICE cannot process truly digital signals, we assume these "digital" signals are converted to analog format before being used by the buffer. Similarly, the tool may require digital signal outputs from the buffer. The specification therefore includes language to define how digital signals supplied or needed by the tool are converted to analog signals compatible with the SPICE model. The D_to_A line specifies the parameters of the digital-to-analog converter the simulation tool should create to connect digital signals from the simulator to analog signals needed by the SPICE model. The trise and tfall parameters signify the rise and fall times, from 0 to 100%, the simulation tool should use for the outputs of the D_to_A converters. Per the specification, [Model]s which use [External Model] may omit the [Pulldown], [Pullup], [POWER Clamp] and [GND Clamp] keywords. However, I should note that any [Model] which uses [External Model] *must* contain the following subparameters and keywords: - Model_type - Vinh, Vinl (as appropriate to Model_type) - [Voltage Range] and/or [Pullup Reference], - [Pulldown Reference], [POWER Clamp Reference], - [GND Clamp Reference], [External Reference] - [Ramp] I hope this helps! - Michael Mirmak Intel Corp. Chair, EIA IBIS Open Forum ________________________________ From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Arnab Hazarika Sent: Tuesday, June 07, 2005 3:18 PM To: ibis-users@eda.org Subject: [IBIS-Users] ibis version4 query Hi all, We are trying to incorporate the [External Model] parameter in ibis models version 4.1.The pdf IBIS ver4.1 example shows an example [Model]Ext_spice_diff_buff [External Model] Language SPICE Corner Typ diffio.spi diff_io_typ Ports A_signal _pos A_signal_neg my_receive my_drive my_enable | D_to_A d_port port1 port2 vlow vhigh trise tfall corner_name D_to_A d_drive my_drive my_ref 0.0 3.3 0.5n 0.3n Typ | [End Model] We had doubt regarding what diffio.spi should contain? Also what does the trise and tfall parameters signify? Moreover if we include [External Model] do we not have to contain the pull up/down,GND/Power clamp? Could someone throw light on this ....Better if someone refers new ibis models where this has been used? Thanks in advance. Best regards arnab hazarika |------------------------------------------------------------------ |For help or to subscribe/unsubscribe, email majordomo@eda.org |with just 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 email a written request to ibis-request@eda.org. | |IBIS reflector archives exist under: | | http://www.eda.org/pub/ibis/email_archive/ Recent | http://www.eda.org/pub/ibis/users_archive/ Recent | http://www.eda.org/pub/ibis/email/ E-mail since 1993Received on Tue Jun 7 09:41:22 2005
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