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Support to resolve warnings on Quartus 2 for Cyclone 4 E device

Honored Contributor I



I am running altera's LCD design on Quartus 2 for Cyclone 4 E device and getting below warnings.Could you please assist to solve these. 



1) "pins must meet Altera requirements for 3.3-, 3.0-, and 2.5-V interfaces. For more information, refer to AN 447: Interfacing Cyclone IV E Devices with 3.3/3.0/2.5-V LVTTL/LVCMOS I/O Systems. 



As per AN447 I did below pin configuration but still getting same warning.CLOCK_50 Location PIN_Y2 Yes 


CLOCK_50 I/O Standard 3.3-V LVTTL Yes 


CLOCK_50 PCI I/O On Yes 




I am not sure whether should I explicit do the assignments for PCI I/O as shown above but in AN 447 its mentioned that "The Quartus II software enables the PCI-clamp diode on the assigned input, bidirectional, or tristated output pins by default using the 3.3/3.0/2.5-V LVTTL/LVCMOS I/O standards" 



2)Warning (332060): Node: CLOCK_50 was determined to be a clock but was found without an associated clock assignment. 

Warning (332061): Virtual clock CLOCK_50 is never referenced in any input or output delay assignment. 

I have generated .sdc file having one constraint "create_clock -name {CLOCK_50} -period 20.000 -waveform { 0.000 10.000 }" 




3) One more Query I am running altera's LCD design in which GPIO pins are assigned as shown below,even when they are not being used in design. My question is why they driven Z even they are not used in design.  

// All inout port turn to tri-state 

assign GPIO = 36'hzzzzzzzzz 






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