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The circuit to be analyzed is described to SPICE by a set of element cards, which define the circuit topology and element values, and a set of control cards, which define the model param- eters and the run controls. The first card in the input deck must be a title card, and the last card must be a .END card. The order of the remaining cards is arbitrary (except, of course, that continuation cards must immediately follow the card being continued).
Each element in the circuit is specified by an element card that contains the element name, the circuit nodes to which the element is connected, and the values of the parameters that determine the electrical characteristics of the element. The first letter of the element name specifies the element type. The format for the SPICE element types is given in what follows. The strings XXXXXXX, YYYYYYY, and ZZZZZZZ denote arbitrary alphanumeric strings. For example, a resistor name must begin with the letter R and can contain from one to eight characters. Hence, R, R1, RSE, ROUT, and R3AC2ZY are valid resistor names.
Data fields that are enclosed in lt and gt signs '< >' are optional. All indicated punctuation (parentheses, equal signs, etc.) are required. With respect to branch voltages and currents, SPICE uniformly uses the associated reference conven- tion (current flows in the direction of voltage drop).
Nodes must consist of least two connections except for transmission line nodes (to permit unterminated transmission lines) and MOSFET substrate nodes (which have two internal connections anyway).