Description
Altera® does not support the use of bus hold input buffers connected to open drain configuration outputs such as CONF_DONE. If it is required to monitor CONF_DONE then use a standard buffer or an input without bus hold on another device or a simple FET to drive an LED.
The circuit within the bus hold input conflicts with the pull up resistor required on the CONF_DONE line. This causes the CONF_DONE edge to be slowed, and may cause configuration to fail.