Siemens Simatic S7-300 CPU 31xC Series User Manual

Glossary
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
Glossary-7
GD circuit
A GD circuit comprises a number of CPUs sharing data by means of global data
communication, and is used as follows:
• A CPU broadcasts a GD packet to the other CPUs.
• A CPU sends and receives a GD packet from another CPU.
A GD circuit is identified by a GD circuit number.
GD element
A GD element is generated by assigning shared global data. It is identified by a unique
global data ID in the global data table.
GD packet
A GD packet can consist of one or several GD elements transmitted in a single message
frame.
Global data
Global data can be addressed from any code block (FC, FB, OB). In particular, this refers to
flag bits M, inputs I, outputs Q, timers, counters and data blocks DB. Global data can be
accessed via absolute or symbolic addressing.
Global data communication
Global data communication is a method of transferring global data between CPUs (without
CFBs).
Ground
The conductive earth whose electrical potential can be set equal to zero at any point.
Ground potential can differ from zero in the area of grounding electrodes. The term reference
ground is frequently used to describe this situation.
Grounding means, to connect an electrically conductive component via an equipotential
grounding system to a grounding electrode (one or more conductive components with highly
conductive contact to earth).
Chassis ground is the totality of all the interconnected passive parts of a piece of equipment
on which dangerous fault-voltage cannot occur.
GSD file
The properties of a PROFINET device are described in a GSD file (General Station
Description) that contains all the information required for configuration.
Just as in PROFIBUS, you can integrate a PROFINET device in STEP 7 using a GSD file.
In PROFINET IO, the GSD file is in XML format. The structure of the GSD file complies with
ISO 15734, the worldwide standard for device descriptions.
In PROFIBUS, the GSD file is in ASCII format.

Siemens Simatic S7-300 CPU 31xC Series Specifications

General

Series	S7-300 CPU 31xC
Power Supply	24 V DC
Communication Interfaces	MPI, PROFIBUS DP
Programming Languages	LAD, STL, FBD, SCL
Operating Temperature	0°C to +60°C
Memory	48 KB - 512 KB
Dimensions	40 x 125 x 130 mm (varies by model)