Siemens SIMATIC S7 Manual page 36

DONE_NDR
ERROR
STATUS_MODBUS
STATUS_CONN
STATUS_FUNC
IDENT_CODE
UNIT
MODBUS / TCP communication via the integrated PN interface of the CPU
2XV9450-1MB02; Manual edition 2.1
The parameter DONE_NDR indicates an error-free execution of the request.
In the operating mode S7 is Client, the activated request was executed
without an error. With a reading function, the response data from the server
has already been entered into the DB. With a writing function, the response to
the request telegram has been received from the server.
In the operating mode S7 is Server, this output indicates a telegram
exchange without errors. In the parameters UNIT, DATA_TYPE,
START_ADDRESS, LENGTH, TI and WRITE_READ the request parameters
of the client are displayed. These outputs are only available and valid as long
as DONE_NDR is TRUE.
When this output is set, an error was recognized.
In the operating mode S7 is Client, the activated request was ended with an
error. The error number is displayed in the STATUS_MODBUS or
STATUS_CONN output.
In the operating mode S7 is Server, an error was detected at a request
telegram of the client or when sending a response telegram. The error
number is displayed in the STATUS_MODBUS or STATUS_CONN output.
When ERROR is TRUE, the STATUS_MODBUS output displays the error
number regarding the processing of Modbus telegrams. The error numbers
are described in section 7.
When ERROR is TRUE, the STATUS_CONN output displays the error
number regarding the processing of the T functions. The error numbers are
described in section 7 and in the STEP7 online help of the functions TCON,
TDISCON, TSEND and TRCV.
Status information like "job processing active" is provided by STATUS_CONN
as well. In this case, the ERROR bit is set to FALSE.
This parameter shows the name of the function, which caused the error
occurred.
With the identification string IDENT_CODE you can order the registration key
at IT4industry. After start-up of the PLC an 18 character string is displayed,
which can be read by means of a variable table?
You can find further information in section 5 "Licensing".
In mode S7 is Client, the parameter UNIT is an input parameter. This input
has to be set according to your requirements. The FB copies this value to the
request telegram and verifies when receiving the respond telegram.
In mode S7 is Server, the parameter UNIT is an output parameter. The FB
copies this value from the request telegram to the respond telegram. The
output is set with the received value when the job is finished without an error.
Function Block MODBUSPN
6-10