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AR# 58944

2013.3 Vivado Implementation - Placement error due to wide-gate shape that straddles module boundaries for modules assigned to different pblocks

Description

A placement error occurs because synthesis (having no insight into pblock alignments) will sometimes infer a wide-gate shape across module boundaries. Then, if the two modules are assigned to different pblocks, the wide-gate shape in not placeable which leads to the following error:

[Place 30-642] Placement Validity Check : Failed to find legal placement.
Reason: Could not place shape in pblock pblock_m_vita49p1_mgt_1.
The unplaced cells are:
Cell m_vita49p1_mgt_1/mux_data[1]_i_179 of type LUT6 placed at site SLICE_X0Y0 (A6LUT)
Cell m_vita49p1_mgt_1/mux_data[1]_i_178 of type LUT6 placed at site SLICE_X0Y0 (B6LUT)
Cell m_vita49p1_mgt_1/mux_data_reg[1]_i_125 of type MUXF7 placed at site SLICE_X0Y0 (F7AMUX)
Cell p_pkt_proc0/pkt_tx/mux_data_reg[1]_i_53 of type MUXF8 placed at site SLICE_X0Y0 (F8MUX)
Cell m_vita49p1_mgt_0/mg_gth_x8_0/GT_GEN[1].gt_GTH_i/mux_data_reg[1]_i_124 of type MUXF7 placed at site SLICE_X0Y0 (F7BMUX)
A special empty cell is placed at site SLICE_X0Y0 (C6LUT) to block the location. This is necessary for shapes of this type
A special empty cell is placed at site SLICE_X0Y0 (D6LUT) to block the location. This is necessary for shapes of this type
Shape dimensions: Width = 1, Height = 1

Solution

The work around is to override the pblock assignments for individual cells (in the XDC file where the modules are assigned to pblocks) so that all members of the wide-gate shape are in the same pblock.
AR# 58944
Date Created 12/20/2013
Last Updated 01/06/2014
Status Active
Type General Article
Devices
  • Kintex-7
  • Artix-7
  • Virtex-7
Tools
  • Vivado Design Suite