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  3. AR# 10143: LogiCORE NCO - The Sin and Cos output of the NCO are off by one clock cycle

AR# 10143

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LogiCORE NCO - The Sin and Cos output of the NCO are off by one clock cycle

Description

I am using the NCO and using the ampi and ampq cos/sin outputs. When I run a functional and post NGDBuild simulation, I see the Cos (ampi) output changing exactly one clock behind the Sin (ampq) output. Am I doing something incorrectly?

Solution


This is how the NCO was designed and you are seeing the expected output
behavior. To "sync" the outputs up, you can add a register to delay the ampi
output so that the Cos and the Sin will change on the same clock edge. You
will have to use the same clock that is used by the NCO.

The DDS will be replacing the NCO; it has the correct behavior, as well as
some extra features.
AR# 10143
Date 12/15/2012
Status Active
Type General Article
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