A custom VLSI design technique, using an integrated CAD system is described. The design system features on the hierarchical design process and layout design capability by system designers (customers). As for application, high-performance LSI's for 16-bit CPU were developed. The LSI design was accomplished in a short period (three months with three designers) due to the hierarchical standard cell approach. The LSI chip contains about 20 K transistors in an 8.84 mm X 8.88 mm die area. High-speed operation (machine cycle = 200 ns) and a high density of 291 transistors/mm2 were obtained with low power consumption (1.2 W) owing to the mixed-MOS type standard cell library and this approach.

The propagation delay time of the ED MOS logic gate is precisely analyzed considering input waveform and loading conditions. According to theoretical consideration and circuit analysis, the rise mode delay time tpLH is approximated as a function of the output capacitance of only the gate concerned. The fall mode delay time t.pHL is determined by the input capacitance and output capacitance of the gate concerned. These results allow the easy implementation of the delay model into a logic simulator. A precise delay simulation is attained by considering the delay components, corresponding to each input node, at the output side of the logic element. The propagation delay times of the transmission gate are precisely analyzed. The operations of the transmission gate are divided into two modes; synchronous mode and asynchronous mode. Corresponding to each mode, the transmission gate, the preceding gate, and the succeeding gate have two kinds of delay times. To simulate delay times of each gate precisely, models which treat these three logic elements as one primitive element in a logic simulator have been proposed. The new timing verification method using the delay model is evaluated with respect to delay-time accuracy and execusion time in a logic LSI. Through this method, circuit simulator accuracy is obtained in the short computer run time of a logic simulator.