CTI 2500-C100, Инструкция по установке и эксплуатации

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CTI 2500 Installation and Operation Guide V2.8 45
4.4.3 Profibus Operation
Operational Mode
Using your programming software you may place the Profibus interface in Stop Mode or in
Operate mode.
•
In Stop Mode, the Profibus interface is not attempting to communicate with slave
devices on the network. No I/O is being updated.
•
When placed in Operate mode, the Profibus interface will attempt to configure and
parameterize the I/O slave devices specified in the Profibus configuration. Assuming
the attempt is successful, the Profibus interface will begin writing outputs and reading
inputs from the slave devices.
When transitioning between modes, the Profibus interface is temporarily placed in Clear
mode. In Clear mode outputs may be cleared (set to a value of off or 0) or not updated. The
action taken depends on Fail-Safe flag in the GSD file for the device and the version of the
Profibus configuration tool used.
If the Fail-Safe flag in the GSD file is set to 0, the outputs will be cleared. If the configuration
tool supports only DPV0 (Siemens COM-PROFIBUS
©)
), the outputs will be cleared,
regardless of the flag setting. In either case, this may cause a bump in the I/O when
transitioning between modes.
If the Fail-Safe flag is set to 1 and the configuration tool supports DPV1 (PLC Workshop
V4.52 and above), the outputs will not be cleared. The status of the slave output will remain
the same or transition to a state defined by the slave device parameterization.
Synchronization Mode
The synchronization mode determines how the Profibus network scan is synchronized with
the 2500 Series controller scan. The Profibus synchronization mode can be set to
Asynchronous or Synchronous.
•
In Asynchronous mode, the controller scan is not synchronized the Profibus network
scan. The controller can write outputs to and read inputs from the Profibus I/O buffer
at any point in the Profibus scan.
•
In Synchronous mode, the controller will wait until all outputs from the previous
controller scan have been written to the slave devices before updating the Profibus
interface with outputs from the current scan.
As long as the Profibus scan is at least 2 times faster than the controller scan, you should
select Asynchronous mode to achieve maximum performance. For example, if the controller
scan time is 30ms, the Profibus scan should be 15ms or less.
If the Profibus scan is less than 2 times faster than the controller scan, it is possible that a
single scan transition of an output could be missed. In this case, you should set the scan
mode to Synchronous or employ programming techniques to ensure that all outputs remain
on for more than one scan.