This attribute records the slot numbers of the cards which the bus
tap is currently configured to transmit cells to. This configuration is
managed automatically, and cannot be changed by the operator. By
examining this attribute for both of a card's BusTap components, it
is possible to determine which bus (if any) the card uses when it
needs to transmits cells to a specific card in the module.
Description of bits:
n0(0)
n1(1)
n2(2)
n3(3)
n4(4)
n5(5)
n6(6)
n7(7)
n8(8)
n9(9)
n10(10)
n11(11)
n12(12)
n13(13)
n14(14)
n15(15)