Gantner IDL 101 - Telegram Format

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IDL 101

COMMUNICATION

HB_IDL101_E_V222.doc

Gantner Instruments Test & Measurement GmbH

10.3.2. Telegram Format

For data transmission via PROFIBUS the following telegram formats are relevant for the

Datalogger IDL 101

Formats with fixed information section length without data field:

SD1 FCSDA SA FC ED

Formats with variable information section length with data field:

SD2 LE DataUnit FCSLEr DA SA FC EDSD2

Formats with fixed information section length with data field:

SD3 DataUnit FCSDA SA FC ED

With PROFIBUS the various telegram formats are differentiated by varying Start-Delimiters (SD). They can also be

called SD1-, SD2- or SD3-telegrams in this context. The telegram formats are valid both for request and response

telegrams. However, a request telegram does not necessarily have to be succeeded by a response telegram of the same

format. In addition to that there is a telegram which consists of only one character and which is used as either positive

or negative acknowledgement, according to the kind of request.

Short Acknowledgement:

: Start-Delimiter (length = 1 byte):

The Start-Delimiter SD identifies the beginning of a telegram. It has the following values in the PROFIBUS-protocol:

format

request telegram response telegram data field length

SD1 hex 10 hex 10 0

SD2 hex 68 hex 68 1 ... 246 (32)

Table 10.12 Start-Delimiter (SD) in the PROFIBUS-protocol

: Length (length = 1 byte):

The Length LE identifies the length of the telegram with variable data field length (SD2-telegram) and comprises the

characters from DA to DataUnit. Thus it corresponds to the length of DataUnit+3 and can have values between 4 and

249.