Siemens SIMATIC S7-1500 Function Manual page 54

Reaction time
The reaction time in the case of cyclic or time-controlled program execution is the time
between the detection of an input signal and the change of a connected output signal.
RT
PROFINET IO with Real Time communication (RT) is the optimal transmission method for
time-critical applications in factory automation. PROFINET IO frames are prioritized over
standard frames in accordance with IEEE802.1Q. This ensures the required determinism in
the automation technology.
Send clock
Period between two consecutive intervals for IRT or RT communication. The send clock is
the shortest possible transmission interval for the data exchange. If IRT is activated for an IO
device, T_DC is equal to the send clock.
Slave
A slave can only exchange data with a master after a request by the master.
→ See also DP slave
STEP 7
STEP 7 is an engineering system and includes programming languages for the creation of
user programs for SIMATIC S7 controllers.
Subnet
Part of a network whose parameters must be coordinated for the devices (e.g. for
PROFINET). A subnet includes the bus components and all connected devices. Subnets can
be connected, for example, using gateways or routers, to form a network.
T_DC
→ See Send clock
User program
SIMATIC differentiates between the operating system of the CPU and user programs. The
user program contains all instructions and declarations as well as data for the signal
processing that enable a plant or process to be controlled. The user program is assigned to
a programmable module (e.g. CPU) and can be structured in smaller units.
Isochronous mode
Function Manual, 10/2018, A5E43884988-AA
Glossary
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