4. Configuration
176
answer the requests. However, for it be a low priority task , it’s not guaranteed that it will run with
that periodicity, because it depends on the CPU load and also on other protocol tasks rivalry.
To help in the compreention of the driver Server IEC 60870-5-104 performance are presented the
result of some test done with a Client 60870-5-104 simulator, connected to a NX3030 running a
Server IEC 60870-5-104.The configured data base was compose of 900 digital points and 100 analog
points ( all with quality and time stamp), and the maintask was using 70ms (of the 100ms interval).
ï‚· Time to complete a general interrogation command: less than one second;
ï‚· Time to transfer 900 digital events + 100 analog events: 6 seconds.
System Performance
In cases where the application has only one MainTask user task responsible for the execution of a
single Program type programming unit called MainPrg (as in Simple Profile), the PLC consumes a
certain amount of time for the task to be processed. At that time we call it as Execution Time.
In an application the average application Execution Time using can be known using the MasterTool
IEC XE in the Device item of its Devices Tree as follows:
PLC Logic-> Application-> Task Configuration in the Monitor tab, Average Cycle Time column.
The user must pay attention to the Cycle Time so that it does not exceed 80% of the interval set in the
MainTask user task. For example, in an application where the interval is 100 ms, an appropriate
Cycle Time is up to 80 ms. This is due to the fact that the CPU needs time to perform other tasks
such as communication processing, processing of the display and memory card, and these tasks take
place within the range (the remaining 20% of Cycle Time).
ATTENTION:
For very high cycle times (typically higher than 300 ms), even that the value of 80% is respected, it
may occur a reduction in the display response time and of the diagnostics key. In case the 80
percentage is not respected and the running time of the user task is closer or exceeds the interval set
for the MainTask, the screen and the diagnosis button cannot respond once its priority in the system
running is lower than the user tasks. In case an application with errors is loaded in the CPU, it may
be necessary to restart it without loading this application as shown in the System Log section.
ATTENTION:
The CPU’s system logs of the Nexto Series (NX3010, NX3020 and NX3030), starting from
firmware version 1.4.0.33 now reloaded in case of a CPU reset or a reboot of the Runtime System,
that is, you can view the older logs when one of these conditions occurs.
I/O Scan Time
For a project that uses digital I/O modules, being them inserted into the bus and declared in the
project, the MainTask time will increase according to the number of modules. The Table 4-113
illustrates the average time that is added to the MainTask:
Declared Modules in the Bus
Added Time in the Main Task Cycle Time (µs)
Table 4-113. I/O Scanning Time
In projects that use remote I/Os, for example, using the NX5001 PROFIBUS-DP Master module, the
manual of the respective module has to be consulted for information about performance and
influences of the module in the execution of user tasks.
To Next Page
Loading...
General