UltraRAM offers a feature called the Auto Sleep Mode that looks ahead to RAM
accesses through a variable-length input pipeline, and dynamically sleeps when none are
pending. When AUTO_SLEEP_TIME is 0 (default), the feature is disabled and no
input pipeline exists. When AUTO_SLEEP_TIME is nonzero (valid only when
MEMORY_PRIMITIVE is UltraRAM), that number of input register
stages is constructed for all module input signals. However, reset ports rst[a|b] will not have any pipeline stages. An equal number of
register stages is required on all inputs for simulation accuracy.