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<== Date ==> <== Thread ==>

Subject: RE: curious OMS58 Problem / Waveform-Size-Limitation
From: johill@lanl.gov (Jeff Hill)
To: "Jens Eden" <eden@bessy2.berlin.ptb.de>, <tech-talk@aps.anl.gov>
Date: Wed, 15 Sep 1999 16:11:52 -0600
> we experienced a strange behaviour of an OMS58 Motor-card.
> If the OMS58-card is jumpered for base address 0xc000, the motor
> suddenly stops, starts again and it needs several retries to reach its
> destination.
> We tried various cards in different crates and this only happens if the
> card has base address 0xc000, even if there are no other cards in the
> crate.
> Anyone an idea, what this could be?

The address 0xc000 sounds suspiciously like the base address for
VXI devices in VME A16. Do you have a VXI device driver or resource
manager installed into your system?

>
> Another question concerns the maximum message size of CA-messages.
> We use Mark Rivers MCA-Record with the Canberra AIM556 MCA, which is
> based on the Waveform-Record. If I try to read more than 4090 channels
> (~16360 bytes), we get the CA-error "data does not fit in a CA-message".
> In caProto.h MAX_MSG_SIZE is defined with 16384 (16*MAX_UDP).
> Is it safe to define MAX_MSG_SIZE at least to 33*1024, (for CA-Server
> and Client)
> or is there another way to do it?
>

In theory, you could increase MAX_MSG_SIZE up to a maximum of 65,535 as long
as you are certain that this change has been compiled into _all_
participating
clients and servers. Note that this change to the source code has not been
tested.

I intend to eliminate this 16k byte barrier in the coming months.

Jeff



References:
curious OMS58 Problem / Waveform-Size-Limitation Jens Eden

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