We are using Cyclone IV Device with part no. EP4CE15F23C8N. We want to use the DIFFCLK_xn/p pins as input pin (to read interrupts) and use this information to implement a logic.
Can DIFFCLK pins be used as Input Signals for Cyclone IV E device?
Yes they can. By default these are the standard dedicated clock input pins and yes, they can be routed to allow them to be read.
FYI - it's pretty quick to create a project, assign one of your input signals to one of these dedicated clock inputs and have Quartus tell you the answer...