The group number included in the N-wire entry. Each group is
identified by two octets.
In the 4-wire mode:
Group1 stands for Port1 and Port2
Group2 stands for Port3 and Port4
Group3 stands for Port5 and Port6
Group4 stands for Port7 and Port8
In the 8-wire mode:
Group1 stands for Port1, Port2, Port3 and Port4
Group2 stands for Port5, Port6, Port7 and Port8