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158 www.xilinx.com Development System Reference Guide
Chapter 8: Physical Design Rule Check
R
DRC Errors and Warnings
A DRC error indicates a condition in which the routing or component logic does not
operate correctly (for example, a net without a driver or a logic block that is incorrectly
programmed). A DRC warning indicates a condition where the routing or logic is
incomplete (for example, a net is not fully routed or a logic block has been programmed to
process a signal but there is no signal on the appropriate logic block pin).
Certain messages may appear as either warnings or errors, depending on the application
and signal connections. For example, in a net check, a pull-up not used on a signal
connected to a decoder generates an error message. A pull-up not used on a signal
connected to a 3-state buffer only generates a warning.
Incomplete programing (for example, a signal without a driver or a partially programmed
logic cell) is reported as an error when the DRC runs as part of the BitGen command, but
is reported as a warning when the DRC runs as part of any other program. The –z option
to the DRC command reports incomplete programming as an error instead of a warning.
For a description of the –z option, see “–z (Report Incomplete Programming)”.