C h a p t e r 1 0 C AN o p e n F u n c t i o n a n d O p e r a t i o n1 0 - 2 110Example 2: read the value of (Index_subindex) 212D_0 in slave of No. 3 through SDO; the data type of(Index_subindex) 212D_0 is double words (32 bits). Request data:PLC device Request messageHigh byte(Hex) Low byte(Hex)D25000MessageHeaderReqID =01 Command =01D25001 Reserved =0 Size =4D25002 Type =01 Node ID =03D25003MessagedataMain index high byte =21 Main index low byte =2DD25004 Reserved =0 Subindex =0D25005 Datum 1=0 Datum 0=0D25006 Datum 3=0 Datum 2=010.4.2 Data Structure of NMT MessageUse the NMT service to manage the CANopen network such as start, operation, reset of nodes, etc.The following table shows the data format of the NMT request message.PLC deviceRequest messageHigh byte Low byteD25000MessageHeaderReqID Command (Fixed to 01)D25001 Reserved Size (Fixed to 04)D25002 Type (Fixed to 03) Node IDD25003 MessagedataReserved NMT service codeD25004 Reserved Node ID Command: Fixed to 01. ReqID: the request ID. Whenever an NMT request message is sent, the message is given a ReqID forthe CANopen master to identify. Before another NMT request message is sent out, the original IDnumber must be changed. In other words, change the value of ReqID. The ReqID range is between00–FF (Hex) to trigger sending the NMA request message. Node ID: the node address for the target equipment on the CANopen network (0: Broadcast). NMT service code:NMT service code (Hex) Function01 Start remote node02 Stop remote node80 Enter the pre-operational state81 Reset application82 Reset communication
