Instruction manual

Connection box C-BOX 300
The C-BOX PROFIBUS protocol implementation
S
ubject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
P
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
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5.6 C-BOX PROFIBUS station address field
The INPUT and OUTPUT buffers keep the information of the selected PROFIBUS
address in this field.
5.7 SAP field
SAP (Service Access Point) is an identifier that is used to share the same
communication channel between processes of two remote stations. This allows
splitting the single PROFIBUS DP service into different services.
The SAP is introduced by Datalogic and it must not be confused with analogous
definitions introduced by PROFIBUS itself.
Datalogic has defined the following values:
Only SAP 255 and 2 are reserved for DPD management. All other SAPs are free and
may be used by new application programs after agreement between the application
programs themselves.
5.8 Length field
The Application layer uses all or a part of the remaining bytes of the Exchange Area
buffers that are not used by the Datalogic PROFIBUS Driver. The Length Field is
introduced to keep the information of how many bytes are really used by the
Application Layer. A fragment that is not the last one of a fragmentation sequence
must fill this field with Max(In/Out)Bytes-4, depending on whether it is an INPUT/
OUTPUT fragment. Otherwise this field is filled with a number that is less than or
equal to Max(In/Out)Bytes-4.
5.9 Application data buffer
The Application data buffer holds useful information processed by the application
program.
5.10 DPD internal queues
C-BOX has two internal queues (one for each direction) to keep the application
events: input queue and output queue.
The input queue is used when a new application event (generally a barcode event)
has to be transmitted from the C-BOX before the Master station has generated all the
acknowledge handshakes for each previous transmission.
The output queue is rarely used at the moment. The implementation of new SAPs (i.e.
• SAP = 0 is act ually used by the slave to transfer acquisition informati on;
it should also be used to transfer application data from Master to
Slave (but this is possible only after agreement between t he
application programs)
• SAP = 2 host mode programming.
• SAP = 255 for Driver Management