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