For 256-level QAM signals, you need 8 input bits, whICh exactly fit the width o f a general-purpose-I/O bank on most microcontrollers. Simultaneously setting all 8 bits ensures synchronization between in-phase and quadrature signals. You CAN eaSILy adapt this circuit for any QAM constellation or DAC resolution. Because this circuit is fully digital, you can also embed it in FPGAs or CPLDs, using the inverters available in the output buffers.

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