RE: TOF trigger busy logics

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From: John Mitchell (John.W.Mitchell_at_nasa.gov)
Date: Mon Mar 24 2003 - 15:34:31 EST

Zhangbu,
Indeed, what you want is the Local BUSY generated in Phillips 794
unit 2-6-4 (set as latch). Unfortunately, the Phillips 794 only has
single GATE and GATEbar outputs. This is the reason that I used the
GATEbar and a 2-fold coincidence to achieve a veto condition for the
TOF logic PULSE unit (2-10-1).

There are two options.

1) Use the TTL or ECL output of the 794 latch. Both are normally
wired internally as GATE (although they can be changed to be DELAY,
DELAYbar, or GATEbar). You will then have to convert to NIM (using
for TTL-NIM, e.g. a LeCroy 688AL or Phillips 726) to provide the veto
for your logic. This option has no effect on the TOFp logic and is
preferable to the other option below. If you do this, you need to
check to make sure that your final NIM signal actually has the same
polarity as the 794 GATE because there is some chance that the 794 is
wired for a different function or that you will make an unintended
polarity change in your logic level conversion. You can set/clear
the 794 latch from the front panel.

2) Add a fan-out at the output of unit 2-6-4. If you choose this
option then you must use a 100% duty cycle fan-out like a LeCroy 429A
or Phillips 740. You cannot use a pulse generating unit like a
discriminator or logic unit as a fan-out for this function. My
preference would be to use a LeCroy 429A or Phillips 740 attached to
the GATEbar output of 2-6-4. (I don't really want to put it on the
GATE output and delay the start of the Local BUSY by an additional
propagation delay.) The normal output of this unit would be
connected to 2-10-1 to provide the input for the 2-fold coincidence
(BUSYbar) just as the direct GATEbar output of 2-6-4 is now. You
would use the OUTbar to give a BUSY signal to your logic. At
present, I don't think there are any fan-out sections available in
the TOFp logic in NIM bin 2, so a fan-out would have to be added in
NIM bin 4.

Let me know what you think.

John

At 1:27 PM -0500 3/24/03, Xu, Zhangbu wrote:
>
>Hi, Frank:
> The BUSY sent to TCD will be taken care of by the TRIGGER.
>What I need probably is the local BUSY from 2-6-4 to
>2-10-2 where the "pretrigger" is BUSY.
>Thanks!
> Zhangbu
>

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