Article ID: 000083665 Content Type: Error Messages Last Reviewed: 04/04/2023

Warning (12620): Input port OE of I/O output buffer is not connected, but the atom is driving a bi-direct

Environment

BUILT IN - ARTICLE INTRO SECOND COMPONENT
Description

Due to a problem in the Quartus® II software versions 14.1 and earlier, you might see this warning when connecting the input of a bidirectional buffer to a constant zero when targeting the Intel® Arria® 10 device family.

The problem occurs due to a synthesis problem in which the OE and IN ports for the bidirectional buffer are switched.

The synthesis problem impacts all other device families. However, the warning is currently only issued for the Intel Arria 10 device family

Resolution

To work around this problem, use the "keep" attribute to preserve the constant wire as shown in the folowing code:

For VHDL:

signal const_zero_sig : std_logic;

attribute keep: boolean;
attribute keep of const_zero_sig: signal is true;

begin

const_zero_sig <= \'0\';

TRI_PIN <= const_zero_sig when ENABLE=\'1\' else \'Z\';

For Verilog HDL:

wire const_zero_sig /* synthesis keep */;

assign const_zero_sig = 1\'b0;
assign TRI_PIN = enable? const_zero_sig : \'bz;


This problem is scheduled to be fixed in a future release of the Quartus II software.

Related Products

This article applies to 3 products

Intel® Arria® 10 SX SoC FPGA
Intel® Arria® 10 GX FPGA
Intel® Arria® 10 GT FPGA