Why does the LTPI_PLL_LOCKED signal of the MAX® 10 LVDS Tunneling Protocol and Interface (LTPI) IP not behave as expected in Quartus® Prime Standard Edition Design Software Version 25.1 and earlier?

Description

When using Quartus® Prime Standard Edition Design Software Version 25.1 or an earlier release, the LTPI_PLL_LOCKED signal of the MAX® 10 LVDS Tunneling Protocol and Interface (LTPI) IP may fail to assert even when the internal PLL has successfully achieved lock.

Resolution

This issue has been fixed in Quartus® Prime Standard Edition Design Software Version 26.1. As a workaround for earlier versions, do not rely on the LTPI_PLL_LOCKED signal to determine the PLL lock status. Instead, monitor the internal signal m10_pll_top_inst_locked, which accurately reflects the lock status of the internal PLL.