In this paper we propose a new design methodology targeted for core-based designs using parameterized macrocells (PMC's). This methodology provides the flexibility for instance-based cores to be easily customized for application requirements. By using few scaling parameters to characterize a PMC, a macrocell can be instantiated in virtually any size depending on the required performance. Moreover, a new first-order macro delay model is proposed which is a function of the scaling parameters of

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... e PMC which enables accurate delay predictions at the subsystem/core level. The proposed delay model is suitable for use by a delay optimizer to determine the optimum scaling parameters of individual PMC's in a core. A PMC library has been developed and used to design cores for communications applications. To demonstrate the effectiveness of the proposed methodology, several subsystems used in a channel LDPC decoder were synthesized using this library where the individual PMC's were optimized for minimum delay. The resulting custom-quality layout have areas ranging from 40 × 100 µm 2 to 380 × 200 µm 2 and delay in the range of 1.6 ns to 10 ns in 0.18 µm, 1.8 V CMOS technology.