Understanding IBIS Conventions

The general syntax of an element card for I/O buffers is:

General Form :

bname node_1 node_2 ... node_N + keyword_1=value_1 ... [keyword_M=value_M]

where:

bname	Buffer element name. Must begin with B, which can be followed by up to 1023 alphanumeric characters.
node_1 node_2 ... node_N	List of I/O buffer external nodes. The number of nodes and corresponding rules are specific to different buffer types (see later sections in this chapter).
keyword_i=value_i	Assigns value, value_i, to the keyword, keyword_i. Optional keywords are given in square brackets (see Specifying Common Keywords for more information).

Figure 19-1: Circuit Diagram for Package

The gnd node on the circuit diagram for buffers denotes the ideal SPICE ground node (the notation node 0 [zero] is also used). This node is always available to Star-Hspice. Do not include this node in the node list on the buffer card. If the gnd node appears on a circuit diagram, Star-Hspice makes the node connection to the ideal ground. Node gnd is used on circuit diagrams to explain the connection of individual parts inside buffers.

In some cases, buffer nodes have different rules than nodes for other Star-Hspice elements. Some nodes may already be connected to voltage sources (Star-Hspice makes such connections) so it is incorrect to connect a voltage source to such nodes. Conversely, some nodes should be connected to voltage sources and it is incorrect not to connect voltage sources to these nodes.

NOTE: See Specifying Common Keywords and the following sections on individual buffer types for detailed explanations on the use of these nodes.

Buffers correspond to models in IBIS files and do not include packages. At this time, corresponding packages should be added manually. For example, if node_out and node_pin are nodes for output of the output buffer and corresponding pin, then add the following lines to the netlist:

R_pkg node_out node_pkg R_pkg_value

L_pkg node_pkg node_pin L_pkg_value

C_pkg node_pin gnd C_pkgvalue

where values for R_pkg, L_pkg, and C_pkg are taken from the IBIS file (see Circuit Diagram for Package for the circuit diagram).

Terminology

The following are definitions of terms used frequently in this chapter:

card, buffer card	Used to denote a line(s) from the netlist that specifies the buffer name (should begin with the letter b), a list of external nodes, required keyword, and optional keywords.
buffer, I/O buffer, input/output buffer	One of 14 IBIS models as specified in the standard, version 3.2, and implemented in Star-Hspice.
RWF, FWF	Rising waveform, falling waveform
I/O	Input/Output
I/V curve	Current-voltage curve
PU, PD	Pullup, pulldown
PC, GC	Power clamp, ground clamp

Limitations and Restrictions

The series, series switch, and terminator buffers are not implemented in the 2000.4 version of Star-Hspice.

You can simulate the terminator by using other existing Star-Hspice elements: resistors, capacitors, and voltage dependent current sources.

Star-Hspice Manual - Release 2001.2 - June 2001