The directed routing constraints (DIRT) used in MPMC v4 for DDR2 MIG PHYs in DDR2 occasionally do not all pass in the PAR report. The following warning occurs:
"# of EXACT MODE DIRECTED ROUTING found:128, SUCCESS:127, FAILED:1
WARNING:ParHelpers:198 - One or more "EXACT" mode Directed Routing constrained net(s) were not successfully routed according to the constraint(s). The router attempted to route the net(s) without regard to the constraint. The number of nets found with Directed Routing Constraints: 128, number successfully routed using the constraints: 127, number failed: 1. The failed nets are listed below. Please use FPGA Editor to determine the cause of the failure.
Net
DDR2_SDRAM/DDR2_SDRAM/mpmc_core_0/gen_v5_ddr2_phy.mpmc_phy_if_0/u_phy_io_0/gen_dq[32].u_iob_dq/stg1_out_rise_0s"
How do I resolve this issue?
Add the following constraint to the design UCF:
AREA_GROUP "DDR_CAPTURE_FFS" GROUP = CLOSED;
This does not affect MPMC2 or MPMC v3 cores.
For more information, see (Xilinx Answer 30129).
This issue is not applicable when generating a MIG UCF from MIG 2.2 or later. To determine the applicability of this issue, check for the lack of the above constraint.