WX_RDB_PB_SZ
wr32(wx, WX_RDB_PB_SZ(0), rxpktsize);
rx_pba = rd32(wx, WX_RDB_PB_SZ(0)) >> WX_RDB_PB_SZ_SHIFT;
fcrth = rd32(wx, WX_RDB_PB_SZ(0)) - 24576;