To get a HIGH(1) output from an XNOR gate, the number of LOW(0) inputs must be odd. Looking at the truth table, TRUTH[0], TRUTH[3], TRUTH[5], and TRUTH[6] fulfill this requirement. This means that these must be HIGH(1) and the rest must be LOW(0), giving the hex value 0x69 to put into the TRUTHn register.
Figure 1. XNOR Gate
