The readback data stream contains configuration frame data that are preceded by 10 words of pipeline data and one frame of pad data, as described in the Configuration Memory Read Procedure (SelectMAP). The readback stream does not contain any of the commands or packet information found in the configuration bitstream and no CRC calculation is performed during readback. The readback data stream is shown in the following figure.
The readback data stream is verified by comparing it to the original configuration frame data that were programmed into the device. Certain bits within the readback data stream must not be compared, because these can correspond to user memory or null memory locations. The location of do not care bits in the readback data stream is given by the mask files (MSK and MSD). These files have different formats although both convey essentially the same information. After readback data has been obtained from the device, either of these comparison procedures can be used.