Data Addressing; Reading/Writing Dp-V1 Telegrams - WEG CFW500 User Manual

Communication between class 2 master and slave (MS2):

Initiates the connection (Initiate)

Data acyclic reading (DS_Read)

Data acyclic writing (DS_Write)

Aborts the connection (Abort)

DP-V1 requests use an SD2 type Profibus DP telegram – with variable data length. This type of telegram has the
following fields:
SD LE LEr
68h xx Xx
SD Telegram start delimiter (Start Delimiter)
LE Telegram length, from the DA field to the DU (Length)
LEr Telegram length repetition (Length repeat)
DA Destination Address
SA Source Address
FC Function Code
DSAP Destination Service Access Point
SSAP Source Service Access Point
DU Data unit, size 1 to 244 (Data Unit for DP services)
FCS Telegram checking byte (Frame Checking Sequence)
ED Telegram end delimiter (End Delimiter)
In this telegram it matters to describe the data structure in the DU field, where the form to access the drive
parameters is defined. The other fields follow the defined by the Profibus specification and, normally, are
controlled by the network master.
5.2.2

Data Addressing

In the functions for reading and writing via acyclic data, these data are addressed with a numbering indicating
which slot and index are being accessed. The slots can be used to address different physical segments of an
equipment (a modular equipment for instance) or even logical segments inside a single equipment. The index
indicates which data inside the segment is being accessed.
5.2.3

Reading/Writing DP-V1 Telegrams

In the Profibus DP protocol, the writing (DS_Write) and reading (DS_Read) DP-V1 telegrams used to access the
parameters have the following structure:
Writing Telegram (DS_Write):
Request
(master -> slave)
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Telegram Header
SD DA SA FC
68h xx xx xx
Profibus Network
Slot 0 Slot 1
Index 0 Index 0
Index 1 Index 1
Index 2 Index 2
... ...
Index 254 Index 254
Figure 5.1: Acyclic Data Addressing
Function
Header
5Fh
Data Unit
DSAP SSAP
xx xx
Slave
... Slot N
Index 0
Index 1
Index 2
...
Index 254
Data Unit (DU)
Slot Index
0 47
Telegram End
DU FCS
xx ... xx
...
Size Request
n Data
(n bytes)
ED
16h
End