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Aimed at the application to processors used in communications networks, three kinds of custom CMOS VLSI chips, each integrating approximately 10 kilogates, were developed. During the development of these chips, we overcame various restrictions on the VLSI design, such as input/output pin limitations, bug correction difficulty, and input/output signal delay. A combination of the software and hardware simulators efficiently eliminated logic errors. Microprogram control memory is placed externally to VLSI chips to facilitate tentative correction of possible remaining errors. Two types of processors sharing uniform architecture were also developed for an overall optimum cost-effectiveness using these VLSI chips. One uses all three kinds of VLSI chips and is suitable for switching and communications processing applications. The other includes one VLSI chip and consists of a single printed circuit board. It is suitable for a portable console processor or a processor imbedded in various equipment. These VLSI processors are being introduced in large numbers in communications networks in Japan.
Date of Publication: Jan 1986