Siemens SIMATIC S7-300 Series Reference Manual page 179

Interrupt, Time-Of-Day-
The TOD interrupt belongs to on of the priority classes for SIMATIC S7 program
processing. It is generated according to a specified date (or daily) and
time-of-day (e.g. at 9:50, hourly, or once a minute). A corresponding organization
block is then executed.
Isolated
The reference potential of the control and load voltage circuits is isolated
galvanically in isolated I/O modules; e.g. with optocouplers, relay contacts or
transformers. I/O circuits can be connected to a common potential.alena
Local data
³ Data, temporary
Load memory
The load memory is part of the central processing unit. It contains objects
generated by the programming device. It is implemented either as a plug-in
memory card or a permanently integrated memory.
Main memory
Main memory is the RAM memory in the ³ CPU, used by the processor for user
program access during program processing.
Master
Masters holding the ³ Token can send/request data to/from other nodes (=
active nodes).
Memory card
Memory cards are card-size memory media for CPUs and CPs, equipped with ³
RAM or ³ FEPROM memory modules.
Module parameters
Module parameters are values which can be used to control the response of the
module. A distinction is made between static and dynamic module parameters.
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
A5E00111190-01
Glossary
Glossary-9