UPGRADE YOUR BROWSER

We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 36553

MIG v3.5, Spartan-3A DSP DDR SDRAM - MAP fails on MIG output design when synthesized using Synplicity

Description

When a MIG v3.5 Spartan3A-DSP design is synthesized using Synplicity, the design fails during the MAP phase of ISE tool implementation.

The MAP failure is due to the "rst_iob_out" component not being packed into an IOB.

This occurs because the clk180 signal is incorrectly pruned away in the "tocontroller" module.

This issue only exists for Spartan-3A DSP DDR designs where the CAS Latency equals 2.5 and the synthesis tool selected is Synplicity.

This issue exists in both Verilog and VHDL designs.

There are no issues with XST designs.

Solution


To work around this issue, a syn_keep attribute must be added to the clk180 signal in the "*controller_0" module.

VHDL Work-around:
Add the following constraint in the *controller_0.vhd" module:

attribute syn_keep : boolean;
attribute syn_keep of clk180 : signal is true;

 
Verilog Work-around:
Update the following in the "*controller_0.v" module:

Existing code:

generate if(CAS_LAT_VAL == 3'b110) begin : FD_INST
(* IOB = "FORCE" *) FD rst_iob_out
(
.Q(rst_dqs_div_int),
.D(rst_dqs_div_d), .C(~clk)
)/* synthesis syn_useioff = 1 */;


Modified code:

wire clk180 /* synthesis syn_keep = 1 */;
assign clk180 = ~clk;
generate if(CAS_LAT_VAL == 3'b110) begin : FD_INST
(* IOB = "FORCE" *) FD rst_iob_out
(
.Q(rst_dqs_div_int),
.D(rst_dqs_div_d),
.C(clk180)
)/* synthesis syn_useioff = 1 */;

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
36211 MIG v3.5 - Release Notes and Known Issues for ISE Design Suite 12.2 N/A N/A
AR# 36553
Date Created 07/02/2010
Last Updated 08/12/2014
Status Active
Type General Article
Devices
  • Spartan-3A DSP
IP
  • MIG