Table of Contents • v
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
4.1.2 Network Architecture – Principles and Regulations .........................70
4.1.2.1 Transmission Media......................................................................71
4.1.2.2 Network Topologies......................................................................73
4.1.2.3 Coupler Modules...........................................................................76
4.1.2.4 Important Terms............................................................................77
4.1.3 Network Communication...................................................................79
4.1.3.1 Protocol layer model.....................................................................79
4.1.3.2 Communication Protocols.............................................................81
4.1.3.2.1 ETHERNET..................................................................................82
4.1.3.3 Channel access method.................................................................82
4.1.3.3.1 IP-Protocol....................................................................................83
4.1.3.3.1.1 RAW IP....................................................................................87
4.1.3.3.1.2 IP Multicast..............................................................................87
4.1.3.3.2 TCP Protocol.................................................................................87
4.1.3.3.3 UDP...............................................................................................88
4.1.3.3.4 ARP...............................................................................................88
4.1.3.4 Administration and Diagnosis Protocols ......................................89
4.1.3.4.1 BootP (Bootstrap Protocol)...........................................................89
4.1.3.4.2 HTTP (HyperText Transfer Protocol) ..........................................90
4.1.3.4.3 DHCP (Dynamic Host Configuration Protocol)...........................91
4.1.3.4.4 DNS (Domain Name Systems).....................................................92
4.1.3.4.5 SNTP-Client (Simple Network Time Protocol)............................92
4.1.3.4.6 FTP-Server (File Transfer Protocol).............................................92
4.1.3.4.7 SMTP (Simple Mail Transfer Protocol) .......................................94
4.1.3.5 Application Protocols ...................................................................94
4.2 MODBUS Functions..............................................................................95
4.2.1 General...............................................................................................95
4.2.2 Use of the MODBUS Functions........................................................97
4.2.3 Description of the MODBUS Functions ...........................................98
4.2.3.1 Function Code FC1 (Read Coils)..................................................99
4.2.3.2 Function Code FC2 (Read Input Discretes)................................100
4.2.3.3 Function Code FC3 (Read multiple registers)............................101
4.2.3.4 Function code FC4 (Read input registers)..................................102
4.2.3.5 Function Code FC5 (Write Coil) ...............................................103
4.2.3.6 Function Code FC6 (Write single register)................................104
4.2.3.7 Function code FC7 (Read Exception Status)..............................105
4.2.3.8 Function Code FC11 (Get comm event counter)........................106
4.2.3.9 Function Code FC15 (Force Multiple Coils).............................107
4.2.3.10 Function Code FC16 (Write multiple registers)........................108
4.2.3.11 Function Code FC23 (Read/Write multiple registers)................108
4.2.4 MODBUS Register Mapping ..........................................................110
4.2.5 Internal Variables ............................................................................111
4.2.5.1 Description of the internal variables...........................................113
4.2.5.1.1 Watchdog (Fieldbus failure).......................................................113
4.2.5.1.2 Watchdog Register:.....................................................................113
4.2.5.2 Diagnostic Functions ..................................................................118
4.2.5.3 Configuration Functions .............................................................118
4.2.5.4 Firmware Information.................................................................120
4.2.5.5 Constant Registers .....................................................................122