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A DRC error indicates a condition in which the routing or component logic will 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 pullup not used on a signal connected to a decoder generates an error message. A pullup not used on a signal connected to a tristate 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 DRC option, see the “-z (Report Incomplete Programming)” section.