|
<< Click to Display Table of Contents >> Navigation: »No topics above this level« NET2000 protocol parameters |
The following table shows the adjustable NET2000 protocol parameters for the device object.
Par. |
Values |
Settings |
Description |
/SA |
1 - 254 |
1 |
Node number for the NET2000 master Example: "/SA=2" |
/RC |
0 - 255, 0 = none |
3 |
Retry counter for errors Example: "/RC=0" |
/TE |
100 - 60000 |
3000 |
Timeout for identification requests (ms) Example: "/TE=1000" |
/TT |
100 - 60000 |
500 |
Timeout for read/write requests (ms) Example: "/TT=100" |
/TQ |
100 - 60000 |
3000 |
Timeout for cross talk (ms) Example: "/TQ=2000" |
/SR |
0 - 3 |
0 |
Suppress identification retry depending on the error. See the following table. Example: "/SR=2" |
In NET2000, PVI has to identify all variables on the PLC (Get OV Service) before they can be addressed (read / write variable data). If an error occurs during identification, PVI retries the identification procedure until the error situation is corrected. For certain system configurations, it is possible that the error status is desired. For example, a PVI application (e.g. visualization) can use variables which will only be created on the PLC in a later system expansion. In this case, the identification of these variables would be repeated continuously and greatly slow down NET2000 communication. Make sure that the PLC identification requests are handled in the idle time. If there is not very much idle time available on the PLC, this will cause additional delays in the NET2000 protocol. The "/SR" parameter can help. With this parameter, identification retries can be suppressed for certain errors.
"/SR=0" |
No suppression (default setting) |
"/SR=1" |
Suppresses error 12601 (variable does not exist on the PLC) |
"/SR=2" |
Suppresses all errors from the PLC (12600 to 12699) |
"/SR=3" |
Suppresses all NET2000 errors except for the communication timeout (error 12510) |
The "/SR=3" setting should only be used sparingly since this could also include errors which could be caused by temporary disturbances on the cable connection. If an error occurs with "/SR" selected, PVI switches the corresponding process object to a continuous error status. This can only be corrected by changing the connection description (CD=...) or by deleting and re-creating the affected process object.
The /RC parameter (retry counter) should first be set to zero ("/RC=0) to set the optimum values of the communication parameters. The parameters for baud rate (/BD parameter) and timeouts (/TE and /TT parameters) are then trimmed. The following basic rule applies: Highest possible baud rate, lowest possible timeout times. The lowest allowed value for timeouts results from the following: Maximum PLC response time + maximum transfer time for 512 bytes + 10 ms (reserve). The /RC parameter (retry counter) can only be set to a higher value when the communication can function without disturbances.
The /TE parameter is only effective when identifying variables (initialization phase) and reading external data types. Variable identification is carried out on the PLC during idle time. As a result, it is important to ensure that there is enough idle time available. If there is not, the /TE parameter has to be increased.
The /TT parameter is effective when reading and writing variable data. On the PLC, write/read services are not processed during idle time, but in a defined task class (NET2000.task_class). In this way, response time can be influenced by the task class being used.
Example of a connection description in good communication conditions:
CD="/IF=com1 /BD=115200 /RC=2 /TE=500 /TT=100 /SR=1"
Example of a connection description in bad communication conditions:
CD="/IF=com2 /BD=38400 /IT=40 /RC=3 /TE=2500 /TT=500 /SR=1"