Siemens S7-400 Installation Manual page 303

Network
In communications, a network is the connection between two or more
S7-400s/M7-400s and other terminals such as a programming device, via a
connecting cable. Data are exchanged over the network between the connected
stations.
Node Number
The node number represents the accessing address of a CPU or programming
device or of another intelligent I/O module when they communicate with each other
via a network. The node number is assigned by the CPU or programming device
using the STEP 7 software.
Non-Isolated
In the case of non-isolated I/O modules, the reference potentials of the control and
load circuits are electrically connected to each other.
O
OB
³ Organization Block
OB Priority
The operating system of the S7-400 CPU differentiates between various priority
classes, for example, cyclic program processing, process interrupt-controlled
program processing. Each priority class is assigned organization blocks (OBs),
where the S7 user can program a reaction. As a standard, the OBs have different
priorities to which they are processed when they occur simultaneously or when
they interrupt each other.
On-Board Silicon Disk
The on-board silicon disk is a memory unit in which all or part of the software of a
CPU 488-4 is stored retentively, including static data.
Operating State
The SIMATIC S7 programmable controllers recognize the following operating
states: STOP, STARTUP, RUN.
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04
Glossary
Glossary-11