i have a question about connecting two HMC767 via 3-wire SPI parallelly (separated LE, CE, shared SCKL, MOSI and MISO).
We tried to connect syntetisators parallelly and we are not able to read data from selected HMC767. We detected voltage collision (on MISO/SDO pin we measure peak voltage cca. 1.6V, the SYNT0 was set as acitive using LE and CE, SYNT0 was disabled (LE,CE))
Writing to both syntetisator was sucessful, and both are locked. But in case of reading R12 (lock detect) reading failed (data were transfered but amplitude were only cca 1.6V).
My idea were changing EnGPO bit in R8 ( 140-00074-00-operating_guide.pdf, Table 17, Reg 08h - analog EN register, bit 5, EnGPO) .
In case if i wanna to read data from SYNT0, i tried to change configuration in R8 to set LD_SDO pin to Z-state on SYNT1 (EnGPO=0). In case if i wanna to read from SYNT1, i will set ENGPO to 1, SYNT0-> EnGPO=1 and reading from SYNT1.
On DK we had no problem using SPI communication, but only with one syntetisator.
Could someone to help us how to config both syntetisators?
Thank you for your response.
You didn't mention which mode you are operating in (see attached). In "open" mode the HMC767's should power up with the SDO's tri-stated. If operating in "HMC or legacy" mode you must write Reg 0x0F[9:8]=11b to tri-state SDO of each device.
Please see page 9 and 10 of the attached document for additional info on reliably selecting the serial interface mode when working with multiple PLL's.
We are using HMC mode for communication and uncontroled MPU on startup - in attached document "figure 7" . Writing only the 0x0F[9:8]=11b we tried, but unsuccessful.
Combination of 0x0F[9:8]=11b and Reg 08h= 0 -> WORKS!
Thank you :-)