The CANopen interface and device profile for IEC 61131-3 programmable controllers (CiA 405) describes two methods of accessing the CANopen network from the PLC (programmable logic controller): network variables and function blocks. The network variables are usually mapped into PDOs to be received or to be transmitted. In the Object Dictionary the IEC 61131-3 variables are accessible in a defined range of indexes. In addition, the profile defines some CANopen-specific function blocks, e.g. for SDO, NMT and Emergency communication services. The profile defines Object Dictionary entries for the configuration, up to 255 resources, and up to 255 tasks.