Siemens Siwarex U, Device Manual

Page: 68 / 89

8BCOMMUNICATION WITH OTHER SYSTEMS
Channel 2
8 *)
Number n for reading DR(n) and DR(n+1) Confirmation of number n for DR(n) and
DR(n+1) prepared for reading
9 *)
Number m for writing DR(m) Status byte
10 *)
Still free Current weight (H) (updated cyclically)
11 *)
Task controlling Current weight (L) (updated cyclically)
12 *)
Variable (H) of DR(m) for writing Current variable (H) corresponding to data
record number n
13 *)
Variable (L) of DR(m) for writing Current variable (L) corresponding to data
record number n
14 *)
Default value for remote display 1 (H)
(transferred cyclically) Current variable (H) corresponding to data
record number n+1
15 *)
Default value for remote display 1 (L)
(transferred cyclically) Current variable (L) corresponding to data
record number n+1
*) for 2-channel module
Table 9-3 Assignment of the peripheral area
9.3 Reading data records from the module
The current weight values are automatically prepared cyclically.
In the area "Current variable" (4 bytes), only the selected data records are read.
Via the number of the data record to be read "n", it is determined which data
records are to be read from SIWAREX U. Here, the specified data record "n" and
the following data record "n+1" are always read and entered in the area "Current
variable".
Via "
Confirmation of the number n for DR(n) and DR(n+1) prepared for reading"
one
should now check whether SIWAREX U has already made available the requested
data records in the area "
Current variable corresponding to data record number n and
n+1"
. (Depending on the cycle time of the automation device, it can take several
CPU cycles before the requested data records are available). If the "
Number n for
reading DR(n) and DR(n+1)"
and the "
Confirmation of number n for DR(n) and DR(n+1)
prepared for reading"
are the same and if it has been established via the live bit that
the component is reacting, then the requested current data records are available in
the area "Current variable".
If a command or writing which changes the content of a data record to be read is
being executed prior to the reading of a data record, then the reading may only be
carried out when the instruction bit and instruction acknowledgement bit for the
writing are the same (i.e. no write task is running or the last write task has ended).
Example:
The command "Adjustment weight valid" affects the data record DR61 (adjustment
digits).
The data record should only be read out when the command has been completed.
When the "
Number n for reading DR(n) and DR(n+1)" does not change, the variables are
prepared anew every 20 ms by the module.
9-60
SIWAREX U