Hi all,
I am attempting to control an ADF4382 PLL over SPI and I have noticed that when the PLL locks, the frequency is often slightly off from what I intended to program. During debugging I have read back the register values after I have written them and I have discovered that the registers 0x0012, 0x0013, 0x0014, which are the registers holding the FRAC1WORD, are not holding the values which I write to the. All of these registers consistently read as 0x00 (their reset values). All other registers which I write to are reading back as the correct, intended value. This essentially means that I will not be able to accurately generate a frequency which is not an integer multiple of my reference.
I thought that maybe I just needed to set the PLL device into 'fractional mode', which I have attempted to do by writing bit2 of register 0x0015 to 0 (which reads back correctly.)
Does anyone know if there is any other reason why I am unable to write just to these specific registers? They are listed as having R/W access, and I haven't been able to find anything specific on the datasheet about controlling access to these registers.
Any guidance would be much appreciated.
Thanks
