IOLTW'99b:

The 1149.1 BST std provides no way to verify the integrity and correctness of scanned data. This may be acceptable for off-line applications, but it is a dangerous feature on-line: we need to have confidence in the string entering or leaving the target IC. Our proposal is to allow the BST controller to read the parity of this string immediately after the scan operation: in case of error, it will be repeated. The proposed method is based only on the four standard TAP pins.