Siemens D7-SYS, Manual

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Communications configuring
System- and communication configuring D7-SYS - SIMADYN D
3-185
Edition 12.2003
NOTE All of the tabular values, which are located in the DB, specified at the
DBNUM input of the WR_TAB, are always transferred.
If the table is too large for a data block, then the tabular values are split-
up into individual sub-sets for transfer. The procedure is as follows:
To start, the first table section is written into the DB and is then
transferred as described above. The LASTDB input of the WR_TAB
remains at 0. The STATUS output of WR_TAB stays at 2 during data
transfer and then changes, at the end of the table sub-set transfer (partial
transfer) from 2 to 1.
The old tabular values in the DB should then be overwritten with the
following tabular values. Once this has been completed, at WR_TAB the
REQDB input should be again set from 0 to 1 to activate the next table
sub-set transfer.
This procedure should be repeated until all of the tabular values have
been transferred.
At the last sub-set transfer, input LASTDB of the WR_TAB should be set
from 0 to 1. This signals the SIMATIC FM application module that data
transfer has been completed. The STATUS output of the WR_TAB then
changes from 2 to 0.
NOTE If there is adequate user memory available, the table can also be saved
in several different DBs. In this particular case, for each table sub-set
transfer, only the matching DB number at the input DBNUM of the
WR_TAB has to be specified. However, it should be ensured that the
DBs are transferred in the correct sequence, so that all of the tabular
values are transferred in an increasing sequence.
The time taken to transfer the tabular values depends on the following
factors:
•
Number of tabular values
•
Size of the data blocks
•
Sampling time of the TAB and TAB_D
•
WR_TAB processing time
In each cycle, a telegram with 56 tabular values is transferred, from the
control to the SIMATIC FM 458 application module.
The time taken for a table to be transferred can be calculated as follows:
Duration of the data transfer = [No. of tabular values / 56] * cycle time of the
slowest FB
(i.e. TAB, TAB_D or WR_TAB)
Table too large for
a DB
Data transfer
duration