Siemens SIWAREX WP231 - Reading Registers

Communication
11.2 Communication via Modbus
SIWAREX WP231
Manual, 07/2014, A5E31238908A-02
155
Table 11- 5 Command mailbox 2: Average priority
Variable
Note
Type
Modbus registers
CMD2_CODE Code of command to be executed USHORT 920
CMD2_TRIGGER Trigger for starting the command USHORT 921
CMD2_STATUS 0=job running; 1=job finished (1 cycle) USHORT 922
CMD2_QUIT 0=no error; <>0=error code USHORT 923
Table 11- 6 Command mailbox 3: Low priority
Variable
Note
Type
Modbus registers
CMD3_CODE Code of command to be executed USHORT 930
CMD3_TRIGGER Trigger for starting the command USHORT 931
CMD3_STATUS 0=job running; 1=job finished (1 cycle) USHORT 932
CMD3_QUIT 0=no error; <>0=error code USHORT 933
11.2.1.4
Reading registers
The method for reading registers depends on whether they belong to the writable data
records (DR 3 to DR 29) or can only be read as current values (DR 30 to DR 34).
If you wish to read the registers from the data records DR 3 to DR 29, you must first export
these as a complete data record to the internal output buffer.
All Modbus registers of the individual parameters can be found in chapter → Scale
parameters and functions (Page 63).
Example
A parameter is to be read from data record 3 (DR 3).
● First, write register CMD3_CODE with 2003 (2000 plus the number of the data record =
read data record).
● Then write CMD3_TRIGGER with "1". The DR3 is then updated in the Modbus buffer
memory.
● It is now possible to read one or more registers with the corresponding variable(s). The
data consistency of the registers read at this time is guaranteed.
You can find all further command numbers in chapter → Command lists (Page 139).
Example
A current measured value is to be read out from DR 30.
⇒ The register can be directly requested because its contents are automatically refreshed in
the SIWAREX module at the specified measuring rate of 100 Hz and are always available
up-to-date.