Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 233)

Glossary
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
Glossary-17
Proxy
The PROFINET device with proxy functionality is the substitute for a PROFIBUS device on
Ethernet. The proxy functionality allows a PROFIBUS device to communicate not only with
its master but also with all nodes on PROFINET.
You can integrate existing PROFIBUS systems into PROFINET communication, for example
with the help of an IE/PB Link or a CPU 31x-2 PN/DP. IE/PB LinkThe IE/PB Link then
handles communication over PROFINET as a substitute for the PROFIBUS components.
See PROFINET Device
RAM
Work memory is a RAM memory in the CPU which is accessed by the processor during user
program execution.
RAM (Random Access Memory) is a semiconductor read/write memory.
Real Time
Real time means that a system processes external events within a defined time.
Determinism means that a system reacts in a predictable (deterministic) manner.
In industrial networks, both these requirements are important. PROFINET meets these
requirements. PROFINET is implemented as a deterministic real-time network as follows:
•
The transfer of time-critical data between different stations over a network within a
defined interval is guaranteed.
To achieve this, PROFINET provides an optimized communication channel for real-time
communication : Real Time (RT).
• An exact prediction of the time at which the data transfer takes place is possible.
• It is guaranteed that problem-free communication using other standard protocols, for
example industrial communication for PG/PC can take place within the same network.
Reduction factor
The reduction rate determines the send/receive frequency for GD packets on the basis of the
CPU cycle.
Reference ground
See Ground
Reference potential
Voltages of participating circuits are referenced to this potential when they are viewed and/or
measured.
Repeater
See Hub