Logic module for generating unequiprobable/random patterns for integrated circuits

US4905241A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Detlef Schmid · Karlsruhe, DE
• Hans Wunderlich · Karlsruhe, DE

Key dates

• Filing date: Nov 13, 1987
• Grant date: Feb 27, 1990
• Expiry date: Nov 13, 2007

Classification

• Technology area (CPC G): Physics
• CPC primary: G06F11/27
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

For assisting the self-test of circuits with unequiplebable random patterns, a logic module is provided which is composed of two types of basic cells. Each basic cell contains a register cell and a sub-circuit composed of gates. Dependent on two control signals, the basic cells can be operated as a normal register, as a shift register or as a linear feedback shift register. In the operational mode as a linear feedback shift register, the logic module can be used as a random pattern generator. To this end, the logic module is divided into a first module and into a second module. The first module contains an interconnection of two types of basic cells and a combinational logic system which operates the one part of the output signals of the basic cell in accordance with a Boolean function. The operational result is supplied to a second module of identical basic cells which operates as a shift register. When a random bit sequence is input into the first module, then all basic cells of the linear feedback shift register are a logical "1" with the probability of 0.5. Following the operation of a portion of the output signals of the basic cells in the combinational logic system, a bit seq…