Experimental Physics and
Industrial Control System

Robert Emery <[email protected]> · Wed, 16 May 2007 17:37:50 -0700

Mark,
My "read" records were each processing at 1Hz. If I slowed down the
"read" rate, I would still see a delay problem with my "set" messages
and that problem would appear at the "read" scan rate.
After I changed the "read" records to be linked with FLNKs I could see
(using wireshark) that "set" messages were able to go out between the
"read" messages and my delay problem was gone as long as I kept the scan
rate of the first "read" record (which started the chain of the FLNKs)
slower that 1 sec.
At 1 sec., the FLNKd chain of 12 "read" records (each record has to
wait about 50 msec for a response) can not finish before the first one
starts the chain again. From the messages that come out it looks like
the message queue is backing up which causes delays for my "set"
messages and causes my "read" messages to also be delayed and out of
sequence.
Unless I can set up more than one port for this device I will have to
live with the >1 sec read rate?
Thanks for your help.
Rob
Mark Rivers wrote:

How are your "read" records being processed. Is each processing at 1Hz, or is it a set of records linked with FNKL links, with only the first record scanning at 1Hz.

If it they were linked then it seems to me that the "set" messages would have to wait for at most one "read" request to process before they went to the head of the queue (since there should be at most 1 read request in the queue. But without testing it I can't be sure.

Mark

________________________________
From: Robert Emery [mailto:[email protected]]
Sent: Mon 5/14/2007 5:26 PM
To: [email protected]
Subject: Asyn Delay

I am using ASYN to communicate with 12 power supplies via an E5810
Ethernet/GPIB gateway from a Linux IOC.  I am periodically (1 sec)
reading 24 parameters from the supplies (voltage and current for each
supply) and am setting the current (3 supplies at a time) when the
operator turns a dial at the console.  The problem that I am having is
that when the current/voltage requests are processed I see about a 1 s
delay in the response to the current set messages.
It takes the power supplies about 50 ms to respond to a request for
current or voltage information.  If these requests are backing up in the
ASYN port queue, I would make sense that I would see this type of delay.
Can I speed up the processing of my current set messages by setting up a
second ASYN port on the same IOC connected to the same gateway?  With a
higher priority?  Or is there a better way to speed up my set messages?
Thanks
Rob Emery
UW Medical Center

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System