An Invalid Cyclic Redundancy Check (ICRC) count indicates that a frame has been received with an invalid cyclic redundancy check value.
A cyclic redundancy check is performed by reading the data, calculating the cyclic redundancy check character, and then comparing its value to the cyclic check character already present in the data. If they are equal, the new data is presumed to be the same as the old data.
If the data is not equal, an error is received and the data is resent.