Description

I am attempting to run timing simulation using NCsim but receive the following warnings:

ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge RST) LOCKED) of instance guido_tb_top.DUT.clk_wiz_v4_3_0_i.inst.plle2_adv_inst of module PLLE2_ADV <./guido_vivado_netlist.sdf, line 537>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.edge_detected_reg of module FDPE <./guido_vivado_netlist.sdf, line 575>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge CLR) Q) of instance guido_tb_top.DUT.sip_slave_top_i.incr_read_reg of module FDCE <./guido_vivado_netlist.sdf, line 593>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.\scl_dly_reg[0]  of module FDPE <./guido_vivado_netlist.sdf, line 677>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.\scl_dly_reg[1]  of module FDPE <./guido_vivado_netlist.sdf, line 695>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.\scl_dly_reg[2]  of module FDPE <./guido_vivado_netlist.sdf, line 713>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.scl_med3_reg of module FDPE <./guido_vivado_netlist.sdf, line 731>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.\sda_dly_reg[3]  of module FDPE <./guido_vivado_netlist.sdf, line 798>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.sda_dly_reg_p of module FDPE <./guido_vivado_netlist.sdf, line 827>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.sda_dly_reg_p_0 of module FDPE <./guido_vivado_netlist.sdf, line 845>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge PRE) Q) of instance guido_tb_top.DUT.sip_slave_top_i.sda_dly_reg_p_1 of module FDPE <./guido_vivado_netlist.sdf, line 863>.
ncelab: *W,SDFNEP: Unable to annotate to non-existent path (IOPATH (posedge CLR) Q) of instance guido_tb_top.DUT.sip_slave_top_i.sda_e_reg of module FDCE <./guido_vivado_netlist.sdf, line 881>.

Solution

Vivado is writing out SDF files that have edge sensitive IOPATH for primitives like FDCE and FDPE.

For example,

(IOPATH (posedge CLR) Q (303.0:380.0:380.0)) 

However, the example "simprim" specify line looks like the following:

(CLR => Q) = (0:0:0, 0:0:0); 

This causes the annotation failure in NCsim timing simulation. 

To eliminate the warnings, you can manually edit the IOPATH line in SDF to remove the positive edge notation:

(IOPATH CLR Q (303.0:380.0:380.0)) 

Note: Vivado Simulator and ModelSim do not complain about the mismatch and can annotate the SDF correctly. 

(posedge CLR => (Q +: D)) = (0:0:0, 0:0:0); 

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