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How to change register settings in HMC704?

Question asked by BTG Employee on Nov 4, 2014
Latest reply on Nov 4, 2014 by DonY

I want to change more register settings than just N, N-fract, and charge pump values.  All of those registers are 24 bits long, whereas others are not (for example, Reg 06h is 23 bits long).  Given that the datasheet specifically says to place 24 data bits on the bus (in HMC SPI mode), should I fill with zeros, for words <24 bits?  And if so, should I fill the LSBs or MSBs?  It’s my understanding that I issue a 0 to indicate a Write cycle, then 6 address bits, then 24 data bits, then the bus goes away after the 32nd clock edge.  But it’s not clear how this would work for words shorter than 24 bits.

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