Article ID: 000073832 Content Type: Troubleshooting Last Reviewed: 08/21/2012

Why do I get oscillations when using either primitive or library of parameterized modules (LPM) latches?


Description MAX 9000, MAX 7000, and FLEX devices do not have latches built into their logic cells. Therefore, the MAX PLUS II software uses combinatorial feedback to implement latches. When complex logic drives the enable input of a latch, the MAX PLUS II software may combine the logic with the latch itself, possibly causing oscillations when simulated with some vectors.

To avoid oscillations, insert an LCELL primitive before the latch to force the MAX PLUS II software to allocate a discrete macrocell or logic element for the latch, separating the latch from the combinatorial logic feeding the gate.

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MAX® 9000 CPLD