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Altera_Forum
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7 years ago

Can I safely ignore warning that output pin cannot be tristated?

Dear all, I have the following code for driving the output and input of my design: Fout_DATA <= DATA; Fout_BE <= BE; Fout_RXF <= RXF; Fout_TXE <= TXE; WR <= Fin_WR; DATA(31 downto 16) <= i...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
7 years ago

Hi,

The issue here is that you are driving a tri-stated signal to a normal IO pin. When the Bidir/Tri signal DATA is tristated ('Z'), the Fout_Data (normal IO) driver can't drive that onto the pin since it is not declared as Tri/Bidir. This kind of logic should ideally not be done in tri/bidir designs as you will loose the Tristate/Bidir functionality of the signal being driven.