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17BTerms and abbreviations
18-6
RTS RTS
=
R
un
T
ime
S
ystem
Run time systems are basic versions of applications. These
minimum versions are supplied with certain products to meet
the prerequisites for the execution of the actual product or to
be able to look at or use results generated by this product on
other processors: making available all routines required to
execute a program in a programming language, e.g. interac-
tions with the operating system, memory requirements, error
routines, inputs and outputs.
SELV SELV
=
S
afety
E
xtra
L
ow
V
oltage
Active parts integrated in SELV circuits must not be con-
nected to ground or protective conductors of other circuits.
They must be safely separated from active parts of higher
voltage.
SELV circuit = secondary circuit (output voltage) which is
rated and protected so that its voltages do not exceed a safe
value in case of correct operation (of the power supply) or in
case of a single fault (of the power supply).
SELV circuits are separated from the input voltage (mains
voltage) by double or enhanced insulation. The voltage value
must not exceed 60 V DC (or 42.4 V AC).
Single slave
→
Slave whose address number may only occur once on the
→
master.
Slave
Passive participant on the bus, only replies on request of the
→
master. Slaves have a clearly defined and unique
→
ad-
dress on the bus. A distinction is made:
•
single slaves whose address numbers may only occur
once on the master and
•
A/B slaves with an A or B being appended to their ad-
dress number which may therefore be present in the
master twice.
Target
The target indicates the target system where the PLC pro-
gram is to run. The target contains the files (drivers) required
for programming and parameter setting.
Unit ID
→
Modbus
Watchdog
In general the term watchdog is used for a component of a
system which watches the function of other components. If a
possible malfunction is recognised, it is either signalled or
suitable program branchings are activated. The signal or
branchings serve as a trigger for other co-operating system
components to solve the problem.
Cycle time
This is the time for a cycle. The following process takes
place:
5. PLC cycle: the PLC program performs one complete run.
6. AS-i cycle: all AS-i slaves are updated (5...10 ms).