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Glossary

S7-400 Automation System Module Data

Reference Manual, Edition 09/2009, A5E00850736-06

461

The permitted input delay depends on the length of the cable between sensor and module.

If, for example, there are long unshielded cables to the sensor (over 100 m), a high input

delay must be set.

Integration time

The integration time is the reciprocal of the → interference frequency suppression in ms.

Interrupt

SIMATIC S7 recognizes 28 different priority classes that control the execution of the

user program. These priority classes include interrupts, such as hardware interrupts. When

an interrupt occurs, the operating system automatically calls an assigned organization block

in which the user can program the required reaction (for example, in an FB).

Interrupt reaction time

The interrupt reaction time is the time from the first occurrence of an interrupt signal to

executing the first statement in the interrupt OB. General rule: Higher priority interrupts are

serviced first. This means that the interrupt reaction time is extended by the program

execution time of the higher priority interrupts and interrupts with the same priority that were

called earlier (queue).

Linearity error

The linearity error indicates the maximum deviation of the measured/output value from the

ideal linear relationship between measured/output signal and digital value. This is specified

as a percentage related to the nominal range of the analog module.

Load memory

The load memory is part of a programmable module (CPU, CP). It contains the objects

generated by the programming device (local objects). It is implemented either as a plug-in

memory card or as integrated memory.

Local data

Local data is the data assigned to a → logic block that is declared in its → declaration section

or in its variable declaration. It includes the following (block-specific): Formal parameters,

→ static data, → temporary data.

Measuring principle, instantaneous value encoding

A module with instantaneous value encoding is always used for extremely fast measurement

methods or for values that change very quickly. With this technique, the module accesses

the variable to be measured as quickly as possible and returns an instantaneous recording

of the signal at a specific time. It should be remembered that due to this measurement

method, the modules are more "sensitive" than the modules using the integrating method. As

a result, interference affecting the measured value can lead to falsification. When using

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Siemens S7-400PLC Especificações Página 461