Glossary •
273
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
Manchester encoding
In this encoding system, a 1 is encoded as a transition from
low
to
high
and a
0 as a transition from
high
to
low
.
Modules
Functions, function blocks and programs are modules.
Each module has a declaration part and a body, the latter being written in
one of the IEC programming languages IL (instruction list), ST (structured
text), SFC (sequential flow), FBD (function block diagram) or LD (ladder
diagram).
MS-DOS
Operating system
, which allows all applications direct access to the
hardware.
O
Open MODBUS/TCP Specification
Specification which establishes the specific structure of a MODBUS/TCP
data packet. This is dependant upon the selected function code.
Operating system
Software which links the application programs to the hardware.
P
Ping command
When a ping command (ping <IP address>) is entered, the ping program
ICMP
generates echo
request
packets. It is used to test whether a node is
available.
Port number
The port number, together with the IP address, forms an unambiguous
connection point between two processes (applications).
Predictable ETHERNET
The delay time of a message on an ETHERNET network can be predicted.
The measures which have been taken in predictable ETHERNET make it
virtually possible to realize realtime requirements.