Warning (18029): Output pin [...] cannot be tri-stated

Hi,

I also have this problem. I'm using Quartus 13.0 and I'm targetting a Cyclone IV GX.

I simplified my design to this:

escc_data_out		<= "00010100";
ESCC_DATA	<= escc_data_out   when blink   = '0' else "ZZZZZZZZ";

ESCC_DATA is also used as an input somewhere in the design.

I get some warning for the whole bus:

Warning (18029): Output pin "pre_syn.bp.ESCC_CTRL_ESCC_DATA_IN_0_" driven by bidirectional pin "ESCC_DATA" cannot be tri-stated

The RTL view seems correct:

https://www.alteraforum.com/forum/attachment.php?attachmentid=8278

However, the post mapping view shows some strange things. Sometimes the blink signal is connected to the tri-state buffer enable pin, sometimes it is connected to the tri-state buffer input.

If I don't use ESCC_DATA as an input, I don't have warnings anymore.

Any idea ?

Franck.