Re: Accomodating I2C and CAN in Hall D control system

[Gerard Visser <gvisser@indiana.edu>]

Hall D Electronics:

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.
>>