  We investigated the equivalence of the T-duality for a bound state of D2 and
D0-branes with the Nahm transformation of the corresponding gauge theory on a
2-dimensional torus, using the boundary state analysis in superstring theory.
In contrast to the case of a 4-dimensional torus, it changes a sign in a
topological charge, which seems puzzling when regarded as a D-brane charge.
Nevertheless, it is shown that it agrees with the T-duality of the boundary
state, including a minus sign. We reformulated boundary states in the RR-sector
using a new representation of zeromodes, and show that the RR-coupling is
invariant under the T-duality. Finally, the T-duality invariance at the level
of the Chern-Simon coupling is shown by deriving the Buscher rule for the
RR-potentials, known as the 'Hori formula', including the correct sign.
