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Re: Accomodating I2C and CAN in Hall D control system



Hall D Electronics:

Hi Gerard,

Perhaps I exaggerated concerning cpu availability, but it certainly is not 100%.  Servers 
required to keep cpu's going may be undergoing maintenance, networks may be down, cpu's 
crash and no one may notice during down periods, etc.  The list is endless.

I know little about I2C, but I've been assuming the master would be some box we buy or 
build, separate from the crate and its contents.

I completely agree that cpu's are not a good choice for any sort of critical 24/7 
monitoring, and autonomous fail-safe systems should be implemented to protect all 
hardware.  But in all cases I'd like to be able to detect that something was shut down 
without having to look at a histogram of detector channel multiplicities.



Gerard Visser wrote:
> Hi Fernando,
>     Apart from any scaler data (which is another issue to discuss), I 
> would think it is desirable to read from each module two temperatures 
> and perhaps four power supply parameters and be able to log or alarm on 
> them. This would amount to, e.g., a total of 12 bytes. These would be 
> read every 10 seconds, perhaps. I don't think this would be a noticeable 
> load on the VME bus, the CPU, or the ethernet. As you note, the VME bus 
> and ethernet will be loaded near maximum, so this is perhaps an 
> additional 0.000001 percent.
>     This would _not_ be an equipment protection mechanism. If the board 
> needs to be shutdown to prevent damage from an overtemperature condition 
> (I don't know that it would need to be, but _if_), then it would be 
> handled locally in the board's hardware. There would be no requirement 
> for high-rel 24/7 monitoring.
>     I would think it prudent that the board temperatures and power 
> parameters are logged while data is taken, because an extreme of 
> temperature or other anomalous condition could affect calibrations.
>     The argument that DAQ CPU is not necessarily available 24/7 I don't 
> really understand... It may be true... But, what else would sit in the 
> crate and be for instance an I2C master, and be guaranteed to work 
> 24/7?? I think it is more realistic just not to require 24/7 
> availability from this sort of controls stuff. In other words it is not 
> to be used for personnel or equipment protection purposes.
> 
>     - Gerard
> 
> p.s. In any case, if the fADC250 and the F1TDC do not require a separate 
> I2C or such controls interface, I think it is a little crazy to require 
> such for the ADC125. I should just provide the parameter reading VME as 
> I intend, and we can always decide not to use that in operations. It 
> will still be worth having for board testing and debugging purposes.
> 
> p.p.s. I put the email list back on - this _is_ a valid topic for 
> discussion amongst all concerned.
> Fernando J. Barbosa wrote:
>> Hi Mark,
>>
>> Earlier, I suggested to Elliott that a document outlining the
>> architecture of the slow controls in Hall D is required, especially for
>> the May review.
>>
>> With regards to the fADC125, which is the bottleneck in DAQ, the
>> occupancy rates can be really high and with 72 ch per module, the
>> backplane transfer rates will definitely be high in regions of the
>> tracking detectors. It may be OK to have the ROC get any monitoring info
>> at some point.
>>
>> Gerard may want to be more explicit as to what parameters he needs to
>> monitor on the fADC125.
>>
>> On the F1TDC and fADC250, the programming parameters are set at startup
>> but there is no temperature monitoring or such.
>>
>> Regards,
>> Fernando
>>
>>
>>
>> Mark M. Ito wrote:
>>> Chris,
>>>
>>> C. Cuevas wrote:
>>>> After talking with Elliott yesterday he explained a few reasons not
>>>> to send the 'housekeeping' values of board temperature, etc in the
>>>> data stream.
>>> Why not?
>>>
>>>  -- Mark
>>>
>>> P. S. Took the email list off the list of addressees.
>>>

-- 

				Sincerely,
					Elliott


================================================================================


  Those raised in a morally relative or neutral environment will hold
		    no truths to be self-evident.
				

Elliott Wolin
Staff Physicist, Jefferson Lab
12000 Jefferson Ave
Suite 8 MS 12A1
Newport News, VA 23606
757-269-7365

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