Instruction manual

Connection box C-BOX 300

The C-BOX PROFIBUS protocol implementation

ubject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany

epperl+Fuchs Group • Tel.: Germany (06 21) 7 76-0 • USA (330) 4 25 35 55 • Singapore 7 79 90 91 • Internet http://www.pepperl-fuchs.com

Date od issue 07/25/2003

5.3 Dynamic PROFIBUS Driver (DPD)

The Dynamic PROFIBUS Driver (DPD) is a layer that is built upon the intrinsic DP

data exchange mechanism. Such a layer is required because the intrinsic DP

PROFIBUS mechanism is not message oriented (a service that otherwise might be

easily obtained if the PROFIBUS FDL layer were available).

PROFIBUS DP could be better seen as a method to share memory between remote

stations.

Anyway the Driver is also needed to add features such as flow control and

fragmentation.

In the following figure the complete Stack is represented:

Figure 5.1 Structure of PROFIBUS driver

The Application Layer is directly above the Dynamic PROFIBUS Driver Layer. This is

true both at the Master (generally a PC or a PLC) and at the Slave side (C-BOX).

5.4 Structure of exchange areas when DPD is used

In order to implement the flow controlled version of the driver, DP Exchange Areas

must be congruently compiled in both directions. INPUT Area is the Exchange buffer

from C-BOX to the Master while OUTPUT Area is the exchange buffer from the

Master to the C-BOX.

Only the first four bytes are used by the Dynamic PROFIBUS Driver layer in both

buffers. These are:

• byte 0: Control Field, used to issue and control the Datalogic PROFIBUS Dri-

ver primitives such as flowcontrol, fragment ation and resynchroni za-

tion;

• byte 1: C-BOX PROFIBUS Station Address Field;

Application program

DPD Layer

Profibus DP

Profibus FDL

RS 485

MASTER (*)

(*) generally PC or PLC

(**) C-BOX

Application program

DPD Layer

Profibus DP

Profibus FDL

RS 485

SLAVE (**)