From: Bruce Hill <bhill@slac.stanford.edu>
To: "image-slac@lists1.slac.stanford.edu"
	<image-slac@lists1.slac.stanford.edu>
CC: "Chaiken, Alison" <alison@slac.stanford.edu>, "Lewis, Stephen A."
	<salewis@slac.stanford.edu>
Date: Fri, 1 Oct 2010 12:21:27 -0700
Subject: Re: EVR and cameras
Thread-Topic: EVR and cameras
Thread-Index: Acthndlfm03JExw2TseMk1Yk/oWFOw==
Message-ID: <4CA634B7.9090304@slac.stanford.edu>
References: <4CA62676.8020703@slac.stanford.edu>
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  Hi Alison,
There's no requirement that the EVR and the framegrabber be in the
same chassis.   I have one IOC with 4 cameras, (2 EDT PCIe8 cards
with 2 cameras each), but since the PMC EVR only has 3 trigger outputs,
I get my 4th trigger from a different EVR.

That said, if you get your EVR trigger from another box, you've increased
the number of boxes that have to be running in order for your camera to
work.

Regarding the trigger rate; you generally do not want to let the triggers
occur more rapidly than you can read out the images.   The UP900 takes
nearly 7ms to read out, and if your trigger pulses are longer or come more
often than that, you get ghost images as the camera triggering gets out of =
sync
with the readout.   Other cameras can read out faster or slower, so you nee=
d
to check your camera specs.

For my EVR's that are dedicated to UP900 cameras, I change the default EVR =
trigger
codes on the EVR control screen to drop codes 140 (full beam), 141 (Beam & =
60Hz),
and 142 (Beam & 30Hz), leaving the fastest available trigger rate 143 (Beam=
 & 10Hz).

- Bruce

On 10/1/2010 11:20 AM, Alison Chaiken wrote:
> Steve, in examining your attached slide, I'm wondering whether EVR cards
> must be plugged into the same chassis as framegrabbers or no.    Wise
> coworkers have advised me that the same PCI bus must host both cards in
> order for the timing system to work properly, although if the camera
> gets a TTL trigger from the EVR, it's not obvious to me that it's
> necessarily so.    I guess that the timing system pulses can be much
> more frequent than the camera acquisition due to long exposures so that
> some care is necessary to figure out which events result in initiation
> of an image acquisition, but I'm not clear on whether there's something
> special about the two cards being on the same PCI bus if a TTL trigger
> is still needed.    I'm still designing my system and am trying to
> understand what my architectural options are.   Thanks!
>