Last bit is the parity of all the data bits _and_ the parity bits, which means it gets
counted as follows (?):
-p6 xx xx xx xx xx xx xx xx xx xx xx xx xx xx
+p6 xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx
Converted to bitmasks:
p3: 01 c7 8f 0f
p4: 00 3f 80 ff
p5: 00 00 7f ff
-p6: 03 b4 e9 86
+p6: 03 b4 e9 96