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Subject: Re: caget command holds for more than 10 seconds
From: Dirk Zimoch <dirk.zimoch@psi.ch>
To: lailongwei <lailongwei@sinap.ac.cn>
Cc: tech-talk <tech-talk@aps.anl.gov>
Date: Tue, 31 May 2011 14:13:38 +0200
lailongwei wrote:
hi,
when I use caget A, though the data has been gotten, it holds for about ten sends untill the command exit. This cause problem when I need to caget four PVs, whose sampling at the same time is very important. How can I solve it.
Thanks!
2011-05-31
------------------------------------------------------------------------
lailongwei

One could argue that strictly speaking sampling over the network is "wrong". TCP and thus CA does not support any real-time behavior. So the best way to solve it is to sample all four PVs on the same real-time IOC. This probably does not help when the PVs are not physically connected to the same IOC. For the future SwissFEL project, we (meaning Babak) took great effort to implement this kind of synchronous data acquisition across multiple IOCs. Our implementation strongly depends on our timing system to synchronize PVs on multiple IOCs. This is nothing you can quickly do with a 'caget a; cage b; caget c; caget d;'

Dirk


Replies:
RE: caget command holds for more than 10 seconds Mark Rivers
References:
caget command holds for more than 10 seconds lailongwei

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