Does DDSM_NCO_PHASE_OFFSET has effect on 31 FFH NCOs in AD9174?

Question

Does anyone know whether DDSM_NCO_PHASE_OFFSET has effect on 31 FFH NCOs in AD9174 main datapath? Thanks.

kberry · Accepted Answer

Hi, the FFH NCOs are implemented through the main NCO, so the phase_offset applied to the main NCO will apply to any FTW currently acting through the main NCO. The phase output when frequency hopping depends on the chosen frequency change mode (reg 0x800[7:6]): in phase discontinuous mode the main NCO is reset each time a new FTW is loaded from one of the 31 FFH banks, in phase continuous mode the main NCO phase continues as is as the new FTW is loaded resulting in a smooth transition into the new frequency. In phase continuous mode the phase accumulator associated with the FFH NCO being loaded is also "loaded" into the main phase accumulator, so the phase will switch to the NCOs current phase. Any offset in DDSM_NCO_PHASE_OFFSET will always apply to the output signal phase.)

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Does DDSM_NCO_PHASE_OFFSET has effect on 31 FFH NCOs in AD9174?