Reduce Bleed Over of Static Nets to the Reconfigurable Pblocks - 2021.2 English

UltraFast Design Methodology Guide for Xilinx FPGAs and SoCs

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2021.2 English

By default, nets in the static region of a DFX design can use any routing resources in the device. However, this might cause the static nets to bleed over to the dynamic region. Although allowed from a functional perspective, this approach reduces the solution space of the router for reconfigurable modules (RMs) inside the reconfigurable partition (RP) Pblock. After the first implementation is complete and static routes and placement are locked using the lock_design command, the static nets are locked with some of the nets in the RP Pblock. During subsequent child implementations, the DFX flow identifies these locked static nets during RM implementation and attempts to perform place and route in a reduced solution space to avoid unroutability. To avoid the bleed over of static nets to RP Pblocks, Xilinx recommends containing the static nets inside a static Pblock by setting the CONTAIN_ROUTING TRUE constraint.

In the following example, the static region Pblock does not have the CONTAIN_ROUTING constraint enabled. The bleed over from the static nets the to RP Pblock is highlighted in yellow. This approach is not recommended, because it negatively impacts routability during RM compile.

Figure 1. Static Region Pblock without CONTAIN_ROUTING Constraint

In the following example, the CONTAIN_ROUTING constraint is enabled on the static Pblock, and there is no bleed over of static nets to the RP Pblock. This is the recommended approach for improved routability during RM compile.

Figure 2. Static Region Pblock with CONTAIN_ROUTING Constraint