Message Format For Cyclic Dp Communication - Siemens SINUMERIK 840DiE sl Manual

8 PROFIBUS DP Communication
8.1 General
Motion Control
extension
8.1.3

Message format for cyclic DP communication

Message frame
structure
Useful data
structure
8-176
2. Slaves (passive nodes)
These devices may only receive messages, acknowledge them and transfer
message to the master on its request.
Examples: Drives, I/O modules
Communication between SINUMERIK 840Di sl (NC and PLC), as the master,
and the slave components on PROFIBUS is based on PROFIBUS DP with the
MotionControl extension.
The MotionControl extension is characterized by:
S
Configurable isochronous DP cycle
S
Cyclic synchronization of the DP slaves using GlobalControl message
frames from the DP master
S
Automatic maintenance of the internal clock by the DP slaves during a short
communication failure between the DP master and DP slave
References: /PPA/ PROFIDrive Profile Drive Technology Version 3,
Draft V1.4.2, 01. September 00
A PROFIBUS message generally adopts the following format for cyclic data
transmission:
Protocol
frame
Parameter identifier
(header)
value (PIV)
Fig. 8-1 Main message format for cyclic data transmission
The useful data for cyclic communication are referred to as parameter process
data objects (PPO). They are subdivided into two areas within the message
frame:
S
Parameter area (PIV, parameter identifier value)
This part of the message frame is for reading and/or writing parameters and
for reading out faults.
S
Process data area (PDA, process data)
In the case of a drive, for example, this area contains the control words, set-
points, or additional information and actual values.
The following data are transmitted with the process data:
– Control words and setpoints (requests: master ––> drive) or
– Status words and actual values (responses: drive ––> master)
Useful data (PPO)
Process data
(PDA)
© Siemens AG 2007 All Rights Reserved
SINUMERIK 840Di sl Manual (HBIsl) – 01/2007 Edition
01/2007
Protocol
frame
(trailer)