Kipp&Zonen COMBILOG Data Logger - Manual (Page 121)

11.7.2 Instruction Set in the PROFIBUS-Protocol
Layer 2-adoption in PROFIBUS protocol:
With PROFIBUS every bus user has so-called "service access
points" (SAPs), via which he can exchange data with the com-
munication partners. With the data logger COMBILOG 1022
the SAPs are used for identifying (addressing) the various data
and commands of the data logger. By specifying the DSAP-
number (DSAP: Destination SAP) in the data field of the re-
quest telegram the data logger can be informed as to which
data shall be transmitted or which function the data logger 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
Hardware Manual COMBILOG 1022
121