& exch2_tNx, exch2_tNy,
INTEGER exch2_tNx( W2_maxNbTiles )
exch2_tNx(I) = 0
tNx = exch2_tNx(myTileId)
exch2_tNx ( tId ) = tNx
iHi = exch2_tBasex(is)+exch2_tNx(is)
tNx = exch2_tNx(tN)