AS-Interface
Command Interface
Subject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
Pepperl+Fuchs Group · Tel.: Germany (6 21) 7 76-0 · USA (3 30) 4 25 35 55 · Singapore 7 79 90 91 · Internet http://www.pepperl-fuchs.com
Issue date - 21.12.2005
28
8 Command Interface
8.1 Construction
If an AS-i slave is addressed in a command or in a response, the address is struc-
tured as shown below
Command byte and T-bit are always part of the response. The T-bit is necessary
to operate the command interface via a MSC1 connection (PROFIBUS
DP V0).
This way the same command of the command interface can be used two twice re
-
peatedly, possibly with different parameters.
The execution of a command of the command interface is declined, if the number
of the transferred parameters is too small which means that the command inter
-
face in the cyclic channel is too small or the DP V1-telegram is too short.
The commands of the command interface are valid as well for PROFIBUS DP V0
as for PROFIBUS
DP V1.Circuit = 0If an AS-i gateway with one AS-i master or the
master 1 of an AS-i
gateway with 2 masters should be choosen.
Circuit = 1 If master 2 of a double master should be chosen.
The commands for reading and writinig exist in two variations. At the first variation
the bits in the slave lists are arranged as usually with Pepperl+Fuchs products:
Data for slave with lower address appear in the lower bits. The second variation is
compatible to Siemens masters: The sequence of the bits in the slave lists bytes
are inverse.
Switching between the two variations can be done with bit 2
6
in byte 2 of the re-
quest. If it is deleted, the Pepperl+Fuchs arrangement is selected, otherwise the
Siemens compatible arrangement is selected.
Request
byte
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1 command
2 T – circuit
3 request parameter byte 1
… …
36 request parameter byte 34
Response
byte
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1 command
2 T result
3 response parameter byte 1
… …
36 response parameter byte 34
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