There is a FITS header variable called wappmask that tells how many wapps were configured and how much data is to be expected in the file for this scan.

Wappmask is a 4 byte unsigned int. The first byte refers to the first wapp. The second refers to the second and so on.

For each wapp there can be 8 possible data streams as there are 2 correlator boards each of which can produce up to 4 streams of data. Each bit refers to one of the expected data streams.

Therefore the number of bits turned on in a byte refers the number of data streams turned on for that wapp. The position of the bit tells you nothing more about the wapp configuration other than the number of streams configured.

For a given byte, the only valid values are:

0x1
0x3
0xf
0xff

Enable WAPP 1 only, no ALFA.

 wappmask
0x00000001 WAPP one only, 1 chan 9-lev, pol a.
0x00000003 WAPP one only, 2 chan 3-lev, auto
0x0000000f WAPP one only, polarization modes

WAPP one and WAPP2, each with 1 chan 9-lev selected.
0x00000101 

All WAPPs enabled with 2 IF channels:
0x03030303

All WAPPs enabled in polarization mode:
0x0f0f0f0f

All WAPPs enabled for ALFA with 2 IF channels per pixel:
0x0f0f0f0f

All WAPPs enabled for ALFA with 1 IF channels per pixel:
0x03030303

All WAPPs enabled for ALFA in polarization mode:
0xffffffff