HMC6300 - spi

Hi everyone,

Anyone knows if there is problem to send 3 bytes (24 bits) to the HMC6300 instead of 18 as shown in the timing diagram of the datasheet (page 14)?

Because most of processor can send only 8 bits... If the component doesn't care to receive more bits than necessary it's fine. But if it's important to send 18 bits and 18 bits only then can anybody recomand me a processor?

Thank you