Saturday, December 31, 2011

Panasonic Ethernet Global Data Sweep Impact





Depending on the association between the Ethernet Global Data (EGD) and CPU sweep time exchange’s period, the data exchange may be transmitted periodically or every sweep after some sweeps number. Consequently, the impact of sweep will fluctuate according to the exchanges number that are listed to be transmitted during the sweep. Nevertheless, at a number of point in the operation of the PLC, all of the replaces will be scheduled to transmit data during the similar sweep. Thus, all exchanges have to be thought when calculating the bad case sweep shock.

The EGD sweep shock has two parts, Production Scan and Consumption Scan, where EGD Sweep Impact = Production Scan Time + Consumption Scan Time Where the Production and Consumption Scans contain of two parts, byte transfer time and exchange overhead where Scan Time = Byte Transfer Time + Exchange Overhead

Exchange Overhead
Exchange overhead contains the time setup for every exchange that will be transmitted during the sweep. This overhead differs dependent on whether the exchange is produced or consumed and if the time stamp for the swap over creates from a remote NTP (Network Time Protocol) server or from the PLC itself. When calculating the sweep shock, comprise overhead time for every exchange.

Time of Byte Transfer
This is the time needed to transmit data between the module of PLC CPU and the module of Ethernet. The time of byte transfer is faintly larger if the memory of PLC being written to could enclose dominates because of supplementary overhead.

Large Ethernet Global Data Configurations Supporting
The VersaMax CPUE05 EGD (Ethernet Global Data) attribute supports a design of up to 32 switches over, at times as short as 10 msecs, with sizes of data as great as 1400 bytes. Nevertheless, the CPUE05 can’t support a design in which each aspect of EGD is exploited. The chart specifies the number of maximum of EGD replaces that the CPUE05 can practically support of a sure size and data restore period under condition of Best-Case s. These numbers will size downwards according to the user program size, the other Ethernet traffic presence of, etc.

The term Best-Case specifies the below setup parameters concern:
• No logic user is attend, so the time of logic sweep is near 0
• There are no modules available in the system.
• No other traffic of Ethernet at hand on the network.
• Imagined timeout of data refresh is 2


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