LMX2581 readback

llya,

I'm not sure that I fully understand, but it seems that you are trying to use the RD_DIAGNOSTICS and comparing this to the pin states.

I am not confident that all these readings are right and readback on the LMX2581 wih Codeloader does not work very well, but we are working on fixing this.

1.   For analog lock detect, typically the output is high with fast narrow pulses when the charge pump comes on.  But if you have open drain output, this would look like 0V if there is no pull-up resistor.  I am not sure what the RD_DIAGNOSTICS word says in this situation, but 0 sounds feasible.

2.  I think that this is right.

3.  If there is any noise on OSCin, then it will set the RD_DIAGNOSTICS to say there is a signal, even if it goes away.  So if RD_DIAGNOSTICS says that OSCin detect =1, then we can't be sure about OSCin.  We can only know that if it reads 0 that there is no signal t OSCin.   The

Regards,
Dean

Dean,

>but it seems that you are trying to use the RD_DIAGNOSTICS and comparing this to the pin states.

Yes, I compare RD_DIAGNOSTICS and RD_DIAGNOSTICS [LD_PIN] for the same parameters. For example:
RD_DIARNOSTICS [16] (OSCIN_DETECT) and RD_DIARNOSTICS [2] (LD_PINSTATE)

>readback on the LMX2581 wih Codeloader does not work very well, but we are working on fixing this.

I do not use CodeLoader. LMX2581 is directly connected to the FPGA.

>But if you have open drain output, this would look like 0V if there is no pull-up resistor. 

"Analog lock detect" is an internal bit in register RD_DIAGNOSTICS. What pin should have pullup to this bit I have been set?

5. VCO_DETECT works as well as FIN_DETECT and OSCIN_DETECT?? manually reset R5[28]???

Ilya,

I was able to read back the word and it seems that the RD_DIAGNOSTICS word is working for me with the exception of VCO_DETECT, FIN_DETECT, and OSCIN_DETECT.However, VCO_DETECT, FIN_DETECT, and OSCIN_DETECT are not particularly useful if they indicate a 1.  The reason that if thre is no input, then there can be self-oscillation, which can trip these detects to indicate a 1. On the other hand, if they indicate 0, then you can conclude no signal.

I was able to get readback working and did some experiments.  What I found is that the VCO_DETECT was always low, and the others always high.  However, the other pins for lock deetct and MUXOUT were working.  Default is the default mode for codeLoader locking at 2.7 GHz.  Then each column after is the change from default  mode.

Regards,

Dean