I have been focusing on Pin 17 it looks like a select pin that is latched externally and seems to only change by pins 3,4 and 6. Also by the links on pin 7,8 and 10. I am thinking its compares the links with 3,4 and 6. Odd thing pin 5 and pin 9 do not have any effect, but is included in circuit. Picture below is quick circuit of Pin 17 output.