Store scalar variables in DSP Adv

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They are not constant and may be written and/or read on any clock cycle.

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if you don't want to use ram then use registers. I don't know if dspbuilder provides enable on registers(delay units), if not so use a mux to enable the path i.e. pass feedback data & new data to a dual inputs mux and select between them according to your write signal, the output of mux goes to a delay unit and fedback to input of mux to keep it if your write is not active.