Siemens Simatic S7-300 Technical Data Manual page 104

Cycle and reaction times
5.5 Interrupt response time
Calculation
The formula below show how you can calculate the minimum and maximum interrupt
response times.
Table 5-14
Calculation of the minimum and maximum interrupt reaction time
Minimum interrupt reaction time of the CPU
+ Minimum interrupt reaction time of the
signal modules
+ PROFINET IO update time (only if
PROFINET IO is used.)
+ DP cycle time on PROFIBUS DP (only if
PROFIBUS DP is used.)
= Quickest interrupt reaction time
Extension of interrupt response times with cyclic PROFINET interconnections
When using cyclical PROFINET interconnections to a remote partner, the interrupt response
time can increase by up to 1.2 ms in addition to the values mentioned above:
• More than 10 cyclical interconnections are configured to the remote partner or
• The interconnection data to the remote partner are greater than 100 bytes.
Signal modules
The process interrupt response time of signal modules is determined by the following factors:
• Digital input modules
• Analog input modules
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 short time can be neglected.
5-22
Process/diagnostic interrupt response times
Process interrupt response time = internal interrupt preparation time + input delay
You will find these times in the data sheet for the respective digital input module.
Process interrupt response time = internal interrupt preparation time + input delay
The internal interrupt preparation time for analog input modules can be neglected. The
conversion times can be found in the data sheet for the individual analog input modules.
Maximum interrupt reaction time of the CPU
+ Maximum interrupt reaction time of the signal
modules
+ 2 x PROFINET IO update time (only if PROFINET
IO is used.)
+ 2 x DP cycle time on PROFIBUS DP (only if
PROFIBUS DP is used.)
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 x n%
n = Setting of the cycle load as a result of
communication
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05