This read-only counter tracks frames received from the frame relay side of an interworked connection that failed translation from RFC 1490 (Frame Relay multiprotocol encapsulation) header format to RFC 1483 (ATM multiprotocol encapsulation) format, because the incoming 1490 header was incorrectly formatted and couldn't be mapped. This flags a specific interworking-function fault where the Frame Relay side is sending headers the ATM interworking function can't parse, as opposed to a generic transmission error, and the description points to cktIWF1490to1483LastBadHeader for the actual bad header bytes to diagnose further. An engineer seeing cktIWF1490to1483Error nonzero on a FR-to-ATM interworked circuit would immediately pull cktIWF1490to1483LastBadHeader to inspect the malformed header and identify which encapsulation the remote FR device is actually using.