Siemens Simatic S7-400 - Manual (Page 620)

Glossary
Glossary-14
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Programming device
A programming device (PG) is an industry-standard, compact personal computer.
A PG is completely equipped for programming SIMATIC programmable
controllers.
Protection level
The SIMATIC S7 access protection concept prevents the central processing unit
from being accessed by unauthorized persons. It has three protection levels:
Protection level 1: all program device functions allowed
Protection level 2: read-only program device functions allowed
Protection level 3: no program device functions allowed
RAM
A RAM (random access memory) is a semiconductor memory with random
access.
RC element
Series connection of ohmic resistance and capacitor. When a load is
disconnected, overvoltage occurs in circuits with inductive load. This can result in
an arc and reduce the lifetime of the contacts. To suppress this arc, you can
bridge the contact with an RC element.
Reboot
In the S7-400: When a CPU starts up, (for example, by switching the mode
selector from STOP to RUN or by switching the power on), either OB 101
(restart) or OB 100 (reboot) is processed before cyclic program scanning (OB 1).
In rebooting, the
³ process input image is read in and the STEP 7 user program
is processed, starting with the first instruction in OB1.
In the M7-400: At rebooting the process input image is read. User programs
continue to be processed and notified about the STARTUP and RUN modes.
Reference ground
³
Ground