arria 10 fpll can not work nomally - arria 10 fpll can not work nomally Hi sir, I am facing one strange problem, details as follows: 1. when I use gxp_dedicated_clock for the reference clock of the transceiver fpll, after power-on, cal_busy signal is low, but the locked signal is not asserted infinitly, I am sure the clock is clean and stable; (Transceive in cascading mode, and the problem at the upstream fpll, i think the problem exists at the downstream fpll yet). Note: when power-on, the reference clock is not my need, firstly, I adjust the clock of the reference clock, then I asserted pll_powedown long time, and the fpll can not work normally; 2. Based 1, I make the fpll work under core mode, and provide the same reference clock, and do the same thing as 1's note, and the fpll can not work normally. When I asserted the pll_powerdown, the fpll can not lock and output the error frequency. 3. after 2, I change the reference clock to lvds io(clk pins), and do the same thing as 2, when I power on, I found the fpll can output correct frequency, and fpll can lock; but when I assert the pll_powerdown and not release, I find the fpll can output correct frequency, and fpll locks stilly; That means, pll can work at reset state, and pll_powerdown has no effect. soft:: quartus 16.0 develope board: a10gx_si_e4 (10gx115s2f45i1sg) example: altclk_ctrl inst_0(.inclk(clk_i), outclk(ref_clk)); fpll_test fpll_test_inst(.outclk0 (outclk), .pll_cal_busy(cal_busy), .pll_locked(clk_locked),pll_powerdown(pll_powerdown), .pll_refclk0(ref_clk)); Could some help me about this problem, thanks. Best regards, Lambert Replies: Re: arria 10 fpll can not work nomally HI, There is known bug on pll_powerdown signal. You can checkout below KDB link https://www.intel.com/content/altera-www/global/en_us/index/support/support-resources/knowledge-base/hsio/2020/why-is-the-assertion-of-pllpowerdown-input-unable-to-reset-the-i.html Thanks. Regards, dlim