9 Oct, 2001

“High speed” FEB-ROD Testing at BNL

Kin Yip

Short report for our FEB-ROD system at BNL taking data at ~ 100 kHz:

Data Integrity

Noise

Continuity

Further studies …

9 Oct, 2001

OC firmware problem solved …Daniel La Marra has provided the latest and greatest version of the firmware for the OC (Output Controller) on the ROD demo board.

Repetitive testing NO more data corruption in using all the 16 MBytes of SDRAM for storing data !

Seems to be the most reliable version so far … and make it possible for us to do what I am going to show here.

16 Mbytes can hold up to 15947 events, each of 263 words --- including some redundant words. These are already many events for one to check data integrity etc.

I have used it to read data at ~100 kHz (which we have checked and verified

using an oscilloscope)

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9 Oct, 2001

Testing at 100 kHz : Noise/Pedestal Run

9 Oct, 2001

Testing at 100 kHz : Fixed Pattern of 0x111

9 Oct, 2001

No missing events …

I have checked that the BCID’s (Bunch Crossing ID) from OC & PU agree with those of FEB except the famous difference of “1”

The BCID would be reset at ~0xdef and one has to take that into consideration when making comparison

All BCID’s come from the same TTC system

For the time being, we use a clock divider to generate triggers at ~100 kHz from the ~40MHz and the trigger of course is synchronous with the clock. I start/stop the trigger by plugging/unpluging a wire.

At trigger rate 100 kHz, we see regular intervals of BCID’s (such as 400 for ~100 kHz) between consecutive events, ie.

eg. BCID(i+1) – BCID(i) = 400 ( in this example and taking care of the 0xdef resetting etc.)

No missing or skipped events At trigger rate 100 kHz, we occassionally see irregular intervals of BCID’s

There are events skipped by the FEB because FEB needs ~9.6 µs for digitization

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9 Oct, 2001

Incidences of discontinuities vs trigger rate

At trigger rate 100 kHz, FEB is quite unstable but I have managed to measure at certain rates

Apparently, events are just skipped at higher rates but the data do not seem to be over-written

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0

50

100

150

200

250

300

350

400

98 103 108 113 118

trigger rates ( kHz)

Inci

denc

es o

f dis

cont

inui

ties

9 Oct, 2001

Comparion of noise measurementsNoise RMS of the pedestals

Not at all surprising because our events are separated by the same time interval and there is no overlap between events

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9 Oct, 2001

“Further studies” …

Our more advanced trigger handling system is coming which would give us significantly more flexibility to control the rates and patterns of triggers through software, and stop the trigger upon BUSY(from ROD) etc.

Two ways for us to take data in sustained mode

Take data at trigger rate of 100 kHz and use just the 16 Mbytes of SDRAM, stop the trigger when the SDRAM is full and start over again when all data in SDRAM is transferred to the disk

Use SLINK and connect it to a PCI board

Develop the necessary calibration codes in the DSP of PU to carry out real calibration using the LAr electronics mock-up at BNL (including FEB, calibration boards etc.)

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