# DSP control PLL chip

Hi:

I meet a problem about PLL chip's controlling .

I use TMS320F28335 (DSP)  to control the HMC833 (PLL) . I have checked the hardware  and  software over and over again.  Both of them are  correct . Furthermore, I confirm the clock of SPI  is lower than 10MHz through delay function . But the signal is still not  appeared.

The same PLL , I use MCU  to   control  it . It output correctly. And I use ARM to control it , the  output is also correct.

MCU,ARM and DSP is different in system clock . The system clock of MCU and ARM  is lower than 30MHz.  The system clock of  DSP is 125 MHz. But I have decreased the clock of SPI  through delay function.

It's worth paying attention to the SPI line, it's guide line soldering and not PCB wiring. Concerning this , I have decrease the SPI clock cycle in 2.5 ms.

I really don't know where I didn't notice . Can you  give me some suggestions.