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Introduction To ProfiBus DP

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Acromag, Inc. Tel:248-624-1541 Fax:248-624-9234 Email:sales@acromag.com http://www.acromag.com

Since there usually is not enough time during the gap to complete a full data

exchange, this process of data retrieval by the class 2 master may continue

over several cycles. At the end of record transfer, the class 2 master will

clear the connection. Note however, that the class 2 master may only

establish communication with the slaves during the gap time.

As stated earlier, it is possible for a class 2 master to temporarily take

over control of a DP slave. During this time, the DP slave will stop its normal

data exchange with its class 1 master. The class 1 master recognizes this

and will proceed to cyclically request diagnostics from the slave, checking

the Master Address field for as long as another valid address is present.

After the class 2 master finishes its communication with the slave, it sets the

Master Address field of the slave to invalid (255). This causes the class 1

master to attempt to regain control of the slave and it will reparameterize and

reconfigure the slave before resuming data exchange with it.

ProfiBus DP –

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Open standard based on EN 50170.

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Fastest Fieldbus standard to date with data rates up to 12MB.

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Plug & play operation.

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Up to 244 bytes of input/output data per message.

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Up to 126 stations may connect to the bus.

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Up to 32 stations per bus segment.

Class 1 Master –

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Central controller that exchanges I/O data with connected slaves.

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Determines the baud rate (slaves auto-detect this rate).

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Manages the token transfer between masters. Detects another

master during the gap time.

Class 2 Master –

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Diagnostic, configuration, or startup tool.

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Can only control one slave at a time.

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Does not have write-access to the slave.

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Does not have a GSD file.

Slave -

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A passive station which can only respond per a master request and

acknowledge messages. A slave has no bus control rights.

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The GSD file defines the slave for the master.

Key Concepts

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