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Glossary

S7-400 Automation System Module Data

458 Reference Manual, Edition 09/2009, A5E00850736-06

Direct data exchange

Direct data exchange is sometimes also known as direct communication. In direct data

exchange, local input address areas of an intelligent DP slave (for example, CPU 315-2 with

PROFIBUS DP attachment) or a DP master are assigned to a PROFIBUS DP partner. The

intelligent DP slave or the DP master receives the input data that the PROFIBUS DP partner

sends to its DP master via these assigned input address areas.

DP master

A node with master functionality in PROFIBUS DP. A master that conforms to IEC 61784-

1:2002 Ed1 CP 3/1 with the DP protocol is known as a DP master. The token allowing

access to the bus is always passed on among the masters. The slaves, in this case DP

slaves, can only react when requested to by a master. The following distinction must be

made:

DP master (class 1): handles user data exchange with the DP slaves assigned to it.

DP master (class 2): Provides services such as: reading input/output data, diagnostics,

global control.

DP slave

A → slave operated on PROFIBUS with the PROFIBUS DP protocol is known as a DP slave.

Equipotential bonding

An electrical connection (equipotential bonding conductor) that ties parts of electrical

equipment and extraneous conductive parts to the same or approximately the same potential

to prevent disturbing or dangerous voltages between these parts.

→ Function block

→ Function

Fiber-optic cable

The "force" function overwrites a variable (for example, memory bit, output) with a value

defined by the user.

At the same time, the variable is write-protected so that the value cannot be modified from

any other location (it cannot, for example, be overwritten by the user program). After

removing the programming device, this value is retained.

The write-protection is canceled only after invoking the "unforce" function, following which

the variable can once again be written with the value set by the user program.

The "force" function can, for example, be used during commissioning to set specific outputs

to the "ON" state for any length of time even if the logic operation in the user program is not

true (due to missing wiring at inputs).

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Siemens S7-400PLC Especificaciones Pagina 458