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AR# 24823

9.1i XST - "FATAL_ERROR:Xst:Portability/export/Port_Main.h:127:1.17"


While running synthesis on the design, I receive the following fatal error:


Why does this occur?


Xilinx is actively trying to provide better error messages to help you debug the issue. Xilinx recommends that you open a webcase at:

and provide a test case that reproduces the problem so that it can be fixed in a future release.

Case 1:

This problem might occur when instantiating IBUF/OBUF/IOBUF in submodules. IBUF/OBUF/IOBUF must be instantiated in the top level of the design.

Case 2:

This might occur when FMAP is being instantiated. You can work around the problem by removing FMAP.

Case 3:

This might occur at the "Advanced HDL Synthesis" step when using dynamic addresses:

reg [15:0] registers [0:7]

assign o_rdata[15:8] = (i_cs & !i_nrw & i_ben[1]) ? registers[i_addr[3:1]][15:8] : 8'h00;"

You can work around the problem by replacing the output assignments o_rdata[15:8] and o_rdata[7:0] with temporary wires. Also, please set the "-signal_encoding" option to "user":

wire [7:0] temp1, temp2;

assign o_rdata[15:8] = temp1;

assign o_rdata[7:0] = temp2;

assign temp1 = (i_cs & !i_nrw & i_ben[1]) ? registers[i_addr[3:1]][15:8] : 8'h00;

assign temp2 = (i_cs & !i_nrw & i_ben[0]) ? registers[i_addr[3:1]][7:0] : 8'h00;

Case 4:

This might occur when XST property "Safe Implementation" is set to "No." To work around the problem, set "Safe Implementation" to "Yes."

Case 5:

To work around the problem, try setting "-signal_encoding" to "user" in Other XST Command Line Options.

Case 6:

This error might occur if there are multiple Asynchronous resets.

For example:

always @(posedge CLK or negedge RESETn or negedge reset_)


always @(posedge CLK or posedge tmp )

where tmp is an intermediate wire, implementing the expected logic
AR# 24823
Date Created 09/04/2007
Last Updated 03/27/2012
Status Archive
Type General Article