What happens if I send the IO_UPDATE asynchronously to the SYNC_CLK?
The IO_UPDATE can be sent asynchronously with one caveat. Sending the IO_UPDATE asynchronously causes the latency through the device to have an uncertainty of +/- one SYNC_CLK period. For example, frequency or phase offset changes will include this uncertainty. Latency is specified as pipe line delay in the data sheet's specifications table. The units are system clock cycles. Pipe line delay or latency is referenced from the rising edge of the IO_UPDATE to when the change appears at the DDS output.
The minimum pulse width of the IO_UPDATE must be greater than one SYNC_CLK period. Typically the SYNC_CLK runs at a fraction of the system clock. The system clock runs at the REF CLK frequency, if the internal REF CLK multiplier (PLL) is disabled. If the REF CLK multiplier (PLL) is enabled, the system clock frequency equals the output of the PLL frequency.
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