Theodor Friedrichs COMBILOG 1020, Hardware Manual

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Hardware Manual COMBILOG 1020
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11.7 Instruction Set in the PROFIBUS-Protocol
Layer 2-adaption in PROFIBUS protocol:
With PROFIBUS every bus user has so-called "service access
points" (SAPs), via which he can exchange data with the commu-
nication partners. With the datalogger
COMBILOG 1020 the
SAPs are used for identifying (addressing) the various data and
commands of the datalogger. By specifying the DSAP-number
(DSAP: Destination SAP) in the data field of the request telegram
the datalogger can be informed as to which data shall be trans-
mitted or which function the datalogger shall carry out. The data-
logger can also be informed as to which own SAP (SSAP: Source
SAP) the data are to be returned.
Request/Response telegram (example SD2-telegram):
SD2 LE
ReqDataUnit
DA
DSAP
LEr SD2 SA FC FCS ED
Data
Data
Data
Data
DSAP
SSAP
DSAP SSAP
SSAP
= 0 = 0
> 0 = 0
= 0 > 0
> 0 > 0
ResDataUnit