Siemens SIMATIC S7-300 Series Reference Manual page 184

Glossary
Start-up
RESTART mode is activated on a transition from STOP mode to RUN mode.
Can be triggered with the ³ Mode Selector Switch or after Power On or with a
PG operation. With an S7-300 a ³ complete restart is performed.
Segment
³ Bus segment
SFB
³ System function block (SFB)
SFC
³ System function
Signal module
Signal modules (SM) form the interface between the process and the PLC. There
are digital modules digital modules (I/O module, digital) and analog modules (I/O
module, analog).
Slave
A Slave can exchange data only on ³ Master request.
System diagnostics
System diagnostics is a method used to recognize, evaluate and report PLC
errors. Examples of such errors: program error or module failure. System errors
can be displayed with LED indicators or in STEP 7.
System Function
This function (SFC) is
³ integrated in the CPU operating system. It can be called as required in the
STEP 7 user program.
System Function Block
The SFB is integrated in the CPU operating system. ³ This function block can
be called as required in the STEP 7 user program.
Glossary-14
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01