questions about sercos iii stack
Dear AJ,
1. how many slaves the minimal 250us cyclic time can support? for the document seems fail to mention this.
2. will the "cross communication" and "NRT" be developed in the future? what is the schedule?
3. in the comx with sercos iii firmware, whether the ieee 1588 module in netx chip is not used?
for the sercos iii uses a different synchron mechanism.
Thank you!
Andreas Jacob
Hilscher Gesellschaft fuer Systemautomation mbH
Hi houzenan,
1) I think there for are currently no values available, otherwise they would be in the documentation :wink:
2) I am pretty sure that Hilscher will implement the features "cross communication" and "NRT". But I have no idea about a schedule.
3) The systime unit is used by the master to produce the actual starting times of MDT/AT (cycle time and AT transmission start time). But not in the way like IEEE 1588 specification defines.
Hi AJ
another question.
For COMX,
In the minimal cyclic time of sercos iii(250us), only MDT0 and AT0 is supported (by comx). MDT1 and AT1~3 are not supported.
Right?
I have refered to the document "SERCOS III Master Protocol API.pdf" ,but the figure 12 "Telegram structure during CP3 and CP4" is too unclear to see.
Hello houzenan,
The SERCOSIII Master supports in CP3 and CP4 up to 4 MDT and up to 4 AT.
Johnny
Thank you Johnny!
whether the "250us" mode also support 4 MDT and 4 AT ? I wanna confirm this.
and could you provide me a clearly printed "figure 12"?
In the document "SERCOS III Master Protocol API.pdf" , the figure 12 (page 65)"Telegram structure during CP3 and CP4" is too unclear to see.
Hello houzenan,
250 us wont be supported with 4 MDT and 4 AT.
Short explenation:
Only if AT0 is completely used (ca. 1500 bytes), AT1 is used.
If additional AT1 is full, AT2 is used.
If additional AT2 is full, AT3 is used.
The same applies for the MDTs.
This means, that at least 9000 bytes are transmitted in each cycle (plus the frame overhead).
One byte needs 80 ns on the Ethernet.
So the frames need more than 720 us. They cannot fit in one bus cycle!
If you want to use short cycle times, than the number of slaves is limited and the amount of process data is limited. I am not able to give here a limit here because this depends on the amount of process data per slave and the length of the optional IP-Channel (NRT-Window).
:D I see. It is very kind of you to reply my questions!
Only 1 master and 5 slaves in my system, and each slave have 10 Byte to send to the master.
We need a cyclic time as short as possible, and 100us is the best.
however, Hilscher's recent stack support shortest 250us .
Similar problem is posted in our bbs by other users as well.
Will Hilscher release a stack with cyclic time less than 250us, or not?
If not, Can it be developed by the customer ?
Hello houzenan,
it is currently not planned to release a master firmware with a cycle time smaller as 250us. There is no technical limitation but small cycle times requires a lot of testing before releasing it.
Please keep in mind, that not all slaves supports cycle times (e. g. drives).
Johnny
Johnny, Thank you for your patience! I see it.
Andreas Jacob
Hilscher Gesellschaft fuer Systemautomation mbH
Hi houzenan,
are you asking for master or slave?