Operation
11
Writing Values (Cyclically)
The description for cyclic writing of one or more values can be
defined in the "User_Prm_Data" of the respective slave through
several subsequent indices. --- Contrary to cyclic reading, the
indices must be entered with a negative sign in the
"User_Prm_Data". -- The order is very important. The output data
are transmitted from the master to the slave in the same order in
which they are defined in the "User_Prm_Data".
Example
The computer output variables of the first two control loops are to
be written cyclically, in the order .L1_YCOMPUTER and
.L2_YCOMPUTER. -
Variable Data type PROFIBUS-DP index
(decimal)
.L1_YCOMPUTER REAL 255
.L2_YCOMPUTER REAL 405
From this results for "User_Prm_Data":
User_Prm_Data = .., .., .., .., -255, -405 End_User_Prm_Data
The 4 bytes at the beginning of the slave-specific parameter data
(.., .., .., ..,) are predefined and must not be used for defining
variables. - Refer to section "Peculiarities of "User_Prm_Data"" for
details. -
To ensure error-free operation, the master must transmit 8 bytes
to the addressed slave. In the first 4 bytes the value for the
.L1_YCOMPUTER variable must be entered (in REAL format),
and in the second 4 bytes the value for the .L2_YCOMPUTER
variable (REAL format as well). -
This example assumes that the necessary configuration
information for the bus system has been provided without errors in
the slave-specific data of the master, and has been accepted by
the addressed slave. -
Refer to section "Addressing the Data" for details about the
assignment of indices to the variables and online parameters, and
for the directives for creating negative indices in hexadecimal
format. --
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