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HMC835LP6GE default & reserved register value

Question asked by sss on Feb 5, 2018
Latest reply on Feb 5, 2018 by dyoung1

Hi all,


Our customer is evaluating the EVAL01-HMC835LP6G.

They have the questions about the register value for HMC835LP6GE.
We are confused, about handling the "reserved" and "default" values!


Reg 01h Chip Enable Register DEFAULT 3h

It is [7:2] = 0 all, default value.

Is it off state ?

off = 0 , on = 1.

Is it correct ?



As for the default "reserved" value in the register map, the content of the description varies.

What does "reserved" mean ?

The "reserved" register is, need to set the value ?, don’t care ?, case by case ? , we are confused !


For example,

It is following, Name;Width;Default;Description.



Reserved;2;2;Reserved, don’t care

Reserved;2;00;Program 00

Reserved;1;1;Program 1





It relates to the above Q2,

it is some different from default value in the "Ultra Wideband Eval Software" to default value in the "register map".


For example, (register map value)

Reg0Bh[23:12] = 78h(Default;7Ch)
Reg19h[23:0] = AB2h(Default;AAAh)



continue,It relates to the above Q2,Q3,


For example, (register map value)

Reg18h[18:0] = 54C1h(Default;54C1h)


It is correct, but datasheet say "Program to 54C3h".

Reserved;19;21697d 54C1h;Program to 54C3h

Our customer checked that it operates without changing the register value of the PLL from the default value to the recommended value.

Is it not recommended ?

Best regards,