40/176 Accessing data on the ID 40/MDT
Bosch Rexroth AG, MIT: ID 40, 3 842 530 344/2014-05
6 Accessing data on the ID 40/MDT
This chapter describes how to access data on the ID 40 system. Data is exchanged
both through the fieldbus interface of the SLK and through the web browser on a PC
connected to the SLK's COM port (see Chapter 10 “Web interface”).
Using a fieldbus system requires a corresponding program running on a PLC,
SoftPLC or other platform with a corresponding fieldbus master module. The ID 40
system itself does not support programming.
The ID 40 system has function blocks for Siemens S7 controllers and Rexroth CL
and PCL controllers to create the programs. See Chapter 14 “Overview for ordering
ID 40 modules” for ordering codes.
Data can be transmitted through the fieldbus either by event or command. Different
fieldbus channels are used that are typically mapped to various I/O address ranges
in the controller.
Accessing the data on the mobile data tag is divided into direct and parameterized
data exchanges. These access types can also be combined. When an MDT enters
the HF field, all parameterized commands are executed first. Data is then either
transmitted directly or the data exchanged with the MDT is automatically terminated.
6.1 Command-oriented data transmission
Command-oriented data transmissions are always initiated by the fieldbus master,
e.g., a PLC. During this, the master sends a command to the SLK. The SLK executes
the command and sends a response to the master. The response always contains the
event code. For read commands, the SLK sends the read data to the master in the
response. Once the response has been sent, the SLK is ready to execute additional
commands.
6.2 Event-oriented data transmission
In event-oriented data transmissions, the data is transmitted by parameterized read
commands from the read/write head to the control system. A new MDT entering
the HF field is the event that triggers the updating of the data. The data sent to the
control system in this manner has to be parameterized beforehand. This is done
using command-oriented data transmissions (Chapter 6.4 “Parameterized data
exchange with MDT”).
6.3 Direct data exchange with MDT
The data on the mobile data tag can be accessed directly through a command-
oriented data transmission as long as the MDT is located within the HF field of the
read/write head. To do this, the control system sends read and write commands
to the read/write head through the fieldbus. The read/write head executes these
commands immediately and sends the result to the control system.
Direct data exchange requires the MDT to be stationary in the HF field.
PROOF COPY 1 | 20.05.2014 | FOR INTERNAL USE ONLY
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