SNAU263A February 2022 – July 2022
Cascaded configurations can be created using the input page, where the relevant VCO buffers and dividers will automatically be enabled by inferring the state of source selection registers.
At least one PLL must always be active and set to XO reference source for cascaded configurations to be valid. APLL start-up priority will automatically choose XO-source APLLs to start up before all other PLLs whenever possible. Start-up priority cannot be properly inferred, therfeore users must set this priority themselves in the User Controls page if in pin-selection mode. In the example image below, APLL3 is referenced to the XO input and APLL1 and APLL2 are referenced from APLL3. Priority is controlled in ascending order, with 0 first and 2 last. APLLs can share priorities; if all APLL priorities are set to 0, all APLLs will start up simultaneously.