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My NOT always enabled tri-state buffers are being removed!

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sebmaster

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Hello,

I am trying to compile my design in Quartus II and keep getting the warning(s):

Warning: Always-enabled tri-state buffer(s) removed
Warning: Converted the fanout from the always-enabled tri-state buffer "Memory_Switch_Lite:inst8|TriState_Unidirectional_Buffer_24Bit:inst26|lpm_bustri:lpm_bustri_component|dout[3]" to the node "MemoryOne_Clock" into a wire
...
and on

But my buffers are not always enabled! They are to switch two memory chips between two inputs/outputs to my program, which buses get which chip is determined by a line connected to an input pin for a uC to control.

I have 'remove redundant logic' in my compiler settings set to 'off' yet still it persists!

Does anyone know how I can keep my buffers?
 

farhada

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Re: My NOT always enabled tri-state buffers are being remove

Hi,
I am not sure your problem is your buffer, the the logic that drives them. Go over you code and make sure that all the signals in your process are assigned a value under reset and under normal condition. Makes sure that all signals are set in both the if and else statements. If you have asynchronous process, make sure that all signals you read are declared in the sensitivity list.

These are small issues, but a lot of times, the error message (or warning) is not the actual problem, but you have to go back and look at the driving signals.

It is possible that your drivers are defined as constant by the program and that is why it removes the buffers.

Hope it helps,
/Farhad
 

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