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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

ProfiBus DP Telegram Header Abbreviations and Frame Bytes

1 byte Start Delimiter (used to distinguish telegram

format).

1 byte Net Data Length (DU) + DA + SA + FC + DSAP +

SSAP.

LEr

1 byte Length

repeated.

1 byte Destination Address– Where this message goes to.

1 byte Source Address – Where this message came from.

The address of the sending station.

1 byte Function Code (FC=Type/Priority of this message).

Used to identify the type of telegram, such as

request, acknowledgement, or response telegrams

(FC=13 signals diagnostic data). See below.

DSAP

1 byte Destination Service Access Point (COM port of

receiver). The destination station uses this to

determine which service is to be executed.

SSAP

1 byte Source Service Access Point (COM port of sender).

1 to 32b

(or 1-244b)

Data Units/ Net Data from 1 to 244 bytes.

FCS

1 byte Frame Checking Sequence (ASIC addition of the

bytes within the specified length).

1 byte End Delimiter (always 16H).

The following picture depicts the telegram sequence between a class 1

master and DP slave. The paragraphs that follow describe each telegram

frame byte in greater detail.

33Tbits

Idle Time

Sync

Time

SD2 LE

rep

SD2 DA

DA SA

FC DU

DU FCS

HEADER

rep

DP MASTER

SD2 SD2

HEADER

TRAILER

DP MASTER

SA FCS

FC ED

DP SLAVE

TRAILER

Immediate

Response

DP SLAVE

SRD Response, DU is Variable Length User Data

TELEGRAM CYCLE w/FRAME

SRD Request (Send & Request Data w/ Acknowledge)

DU is Variable Length User Data

INPUT DATA

REPONSE FRAME

TELEGRAM CYCLE

OUTPUT DATA

REQUEST FRAME

The Start Delimiter identifies the beginning of a telegram and its general

format. ProfiBus DP uses four types of Start Delimiters (SD) for request and

response telegrams, plus a fifth response for a short acknowledgement as

shown below. Note that the short acknowledge response does not use a

start delimiter. Also, a telegram response does not have to use the same

Start Delimiter as the request telegram.

Start Delimiter (SD)

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 37 38

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