[etherlab-dev] EtherCat performance

Niranjan Reddy kniru.reddy at gmail.com
Fri Mar 19 03:18:49 CET 2010

Hi all,
                   We have developed EtherCat master stack for one of our
RTOS (vxworks) CPU. We are able to send and receive ethercat Frames to slave
nodes connected in direct mode to our master.

 I would like know some valuable information regarding EtherCat performance.

As per my knowledge EtherCat performance mainly depends on payload data
which is sent in the EtherCat frame. I would like to know
Do any other factors or components affect the etherCat performance? Like

1. Does the performance depend on the Ethernet controller which is used?
2. Does the performance depend on the network topology?
3. What are components (like PHY delay, slave forwarding delay and any other
components) to be considered while calculating the EtherCat cycle time?
4. What are distributed clocks? If distributed clocks are used can this help
in improving the performance.

I need the above information because Twin cat supports hard real time
capabilities for only Intel based PCI cards.

But in my project we are using
1. PPC 8347 three speed Ethernet controller.
2. Micrel KS8721BL/SL PHY
Will this affect my actual performance?
I heard that the performance is affected by type of Ethernet controller
chip? Is that correct?

I ‘m very much concerned about this because when I send a shared payload
data (3 commands LRW,LWR,LRD) of 49 bytes to 3 different  Slave I/O devices
(digital output and analog input slave devices) my actual EtherCat cycle
time achieved
is 38 to 40 us (micro seconds) but the expected result according to IEEE
report says that it just take 17 us(micro seconds).

Please give me your valuable suggestions which can help me in sorting out my
performance issue.
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