Siemens SIMATIC S7-300 CPU Data: CPU 315-T-2 DP User Manual

Cycle and response times
7.2 Cycle time
Physical cycle time depending on communication load
The figure below describes the non-linear dependency of the physical cycle time on
communication load. As an example, we have chosen a cycle time of 10 ms.
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Figure 7-4 Dependency of the Cycle Time on the Communication Load
Influence on the physical cycle time
Due to the increase in the cycle time as a result of the communications component, even
more asynchronous events occur, from a statistical point of view, within an OB 1 cycle than,
say, interrupts. This further extends the OB1 cycle. This extension depends on the number
of events that occur per OB1 cycle and the time required to process these events.
Note
Change the value of the "communication load" parameter to check the effects on the cycle
time at system runtime. You must consider the communication load when you set the
maximum cycle time, otherwise timing errors may occur.
Tips
• If possible, apply the default value.
• Increase this value only if the CPU is used primarily for communications and if the user
program is not time critical.
• In all other situations you should only reduce this value.
S7-300 CPU Data: CPU 315T-2 DP
7-8 Manual, 12/2005, A5E00427933-02

Siemens SIMATIC S7-300 CPU Data: CPU 315-T-2 DP Specifications

General

Programming Language	STEP 7
Power Supply	24 V DC
Number of DP masters	1
Processable Technology objects	Yes
Number of counters	256
Number of timers	256
S7 communication	Yes
Number of connections for S7 communication, max.	16
PG/OP communication	Yes
Global data communication	Yes
Integrated DP interface	Yes
Integrated PROFINET interface	No
SIMATIC Computing Platform	No
Operating Temperature	0 to 60 °C
Integrated Interfaces	MPI, DP
Communication	PROFIBUS DP
Cycle Time	0.1 ms
Engineering with	STEP 7
Backup available	Yes
Transmission rate, max.	12 Mbit/s