Repack Design Constraints (.xml)

Warning

For the best practice, current repack design constraints only support the net remapping between pins in the same port. Pin constraints are NOT allowed for two separated ports.

• A legal pin constraint example: when there are two clock nets, clk0 and clk1, pin constraints are forced on two pins in a clock port clk[0:2] (e.g., clk[0] = clk0 and clk[1] == clk1).

• An illegal pin constraint example: when there are two clock nets, clk0 and clk1, pin constraints are forced on two clock ports clkA[0] and clkB[0] (e.g., clkA[0] = clk0 and clkB[0] == clk1).

An example of design constraints is shown as follows.

<repack_design_constraints>
  <pin_constraint pb_type="clb" pin="reset[0]" net="rst_n"/>
  <pin_constraint pb_type="clb" pin="clk[0]" net="clk0"/>
  <pin_constraint pb_type="clb" pin="clk[1]" net="clk1"/>
  <pin_constraint pb_type="clb" pin="clk[2]" net="OPEN"/>
  <pin_constraint pb_type="clb" pin="clk[3]" net="OPEN"/>
  <ignore_net name="rst_n" pin="clb.I[0:11]"/>
</repack_design_constraints>

Pin constraint

pb_type="<string>"

The pb_type name to be constrained, which should be consistent with VPR’s architecture description.

pin="<string>"

The pin name of the pb_type to be constrained, which should be consistent with VPR’s architecture description.

net="<string>"

The net name of the pin to be mapped, which should be consistent with net definition in your .blif file. The reserved word OPEN means that no net should be mapped to a given pin. Please ensure that it is not conflicted with any net names in your .blif file.

Warning

Design constraints is a feature for power-users. It may cause repack to fail. It is users’s responsibility to ensure proper design constraints

Ignore net

To ignore the global nets on specific pins, use the syntax ignore_net. Note that the qualified pins are inputs, outputs, and clocks of pb_type. The option is useful for preventing global nets from being assigned to unwanted pins on pb_type.

name="<string>"

The global nets’s name to be ignored, which should be consistent with user-defined global nets in the PCF file.

pin="<string>"

The specified pins on a certain programmable block, which should be consistent with VPR’s architecture description.