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

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Cycle and response times

7.5 Interrupt response time

Calculation

The formulae below show how you can calculate the minimum and maximum interrupt

response times.

Table 7-8 Process/diagnostic interrupt response times

Calculation of the minimum and maximum interrupt reaction time

Minimum interrupt reaction time of the CPU

+ Minimum interrupt reaction time of the

signal modules

+ DP cycle time on the PROFIBUS DP

= Quickest interrupt reaction time

Maximum interrupt reaction time of the CPU

+ Maximum interrupt reaction time of the signal

modules

+2 x DP cycle time on the PROFIBUS DP

The maximum interrupt reaction time is longer when

the communication functions are active. The extra

time is calculated using the following formula:

tv: 200 μs + 1000 μs × n%

Significant extension possible with n = cycle time

extension through communication

Signal modules

The process interrupt response time of signal modules is determined by the following factors:

• Digital input modules

Process interrupt response time = internal interrupt preparation time + input delay

You will find the times in the data sheet of the digital input module concerned.

• Analog input modules

Process interrupt response time = internal interrupt preparation time + conversion time

The internal interrupt processing time of the analog input modules is negligible. The

conversion times can be taken from the data sheet of the analog input module

concerned.

The

diagnostic interrupt response time of signal modules is equivalent to the period that

expires between the time a signal module detects a diagnostic event and the time this signal

module triggers the diagnostic interrupt. This time is so small that it can be ignored.

Process interrupt processing

When the process interrupt OB 40 is called, the process interrupt is processed. Interrupts

with higher priority interrupt process interrupt processing and direct access to the I/O is

made when the statement is executed. When process interrupt processing is completed,

either cyclic program processing is continued or other interrupt OBs with the same or a lower

priority are called and processed.

S7-300 CPU Data: CPU 315T-2 DP

7-16 Manual, 12/2005, A5E00427933-02

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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