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CMS Tracker Synchronization
K. GillCERN EP/CME
B. Trocme, L. MirabitoInstitut de Physique Nucleaire de Lyon
[email protected] LECC 2003 CMS Tracker Synchronization
Outline
Timing issues in CMS Tracker
Synchronization method
Relative synchronizationSynchronization of readout chain across all channels in system
Absolute synchronizationSynchronization with LHC collisions and rest of CMS.
Monitoring synchronization
[email protected] LECC 2003 CMS Tracker Synchronization
CMS Silicon Strip Tracker
Unprecedented use of microstriptechnology. Enormous system.
210m2 silicon10 million channels
Must be very well synchronized to be able to detect, reconstruct and measure particle tracks with expected precision
~25 m3
[email protected] LECC 2003 CMS Tracker Synchronization
CMS Tracker readout and control parts
Not only large amount of silicon. Rest of system also large and complex.
All parts now defined and in production
Starting to look in detail at final system aspects calibration and synchronization
digitaloptical link
Optical transmitter
�����
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�������������
ADC
RAMTTCrx
TTCrx µPFront End Driver
T1
Front End Controller
I2C
Front End ModuleDetector
Control module
PLL
CLK
CCU������������������������
��
������
analogueoptical link
DCU
Tx/Rx
Tx/Rx
APV
APVMUX
256:1
FPGA
FPGA
25k sensors, 17k modules
75k APVs
17k AOHs
3000km fibres
320 mFECs
440 FEDs
[email protected] LECC 2003 CMS Tracker Synchronization
timing issues: components
DOH
CCUM
CCUM
CCUM
CCUM
CCUM
CCUM
CCUM
TPLL
APV
Digital optical control link
Analogue optical readout link
FEC
FED
TTCrx
TTCrx
LHCCK
T1,RST,CAL
Front-end
Back-end
TTC
AOH
FEH
CCUM
control ring
[email protected] LECC 2003 CMS Tracker Synchronization
timing issues: cable delays (rough estimates)
DOH
CCUM
CCUM
CCUM
CCUM
CCUM
CCUM
CCUM
TPLL
APV
FEC
FED
TTCrx
TTCrx
LHCCK
T1,RST,CAL
Front-end
Back-end
TTC
AOH
FEH
CCUM
~2ns
~2ns
~2ns
~2ns
~2ns
~2ns
~2ns
~2ns
~2nsvariable length ~200-300ns
variable length ~200-300ns
~50ns
~50ns
[email protected] LECC 2003 CMS Tracker Synchronization
Tracker timing issues - front-end APVs
DOH
CCUM
CCUM
CCUMCCUM
CCUM
CCUM
TPLL
APV
Goal is to synchronize all APVs in Tracker relative to LHC collisions
AOH
(a) APV output in ‘peak’ mode
Signal is broad, synchronization to ~25ns OK
(b) ‘deconvolution’ mode at high luminosity
Peak now narrow, require few ns synchr.
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CCUM
CCUM
adjustable timing skew
( Also, APV latency must be set correctly to read data from correct pipeline location)
data
FEH
TTCSlow ctl
[email protected] LECC 2003 CMS Tracker Synchronization
Timing issues: back-end (FEDs)
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6.05.04.03.02.01.00.0Time (μs)
FEDs must also be well synchronized
Delay FPGA before front-end FPGACoarse clock skew (25ns steps)
to analyse same APV sample across whole set of 12 inputs
Fine clock skew (1ns steps) to allow enough settling time (readout b/w<100MHz)Need to set to be ~20ns after start of signal pulse
(a) APV signals at FED after trigger
(b) Zoom on ticks
2x128 analogsamples
Digital header
APV ticks
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Am
plitu
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nts)
7550250-25Time (ns)
Optimum sampling point
[email protected] LECC 2003 CMS Tracker Synchronization
CMS Tracker synch requirements summary
Fine (3ns)Fine (3ns)Optical link sampling at FED
Fine (3ns)(deconvolution)
Coarse (25ns)(peak mode)
APV sampling of detector signals
Same clock cycle (25ns)
Same clock cycle (25ns)
APV frame finding at back-end FED
Correct bunch crossing (25ns)
Correct bunch crossing (25ns)
APV trigger latency setting
High luminosity running
Low luminosity running
Synchronization requirement
[email protected] LECC 2003 CMS Tracker Synchronization
Tracker relative synchronization procedure
Method proposed after experience in 25ns test-beam in 2000
Based on measurement of time of arrival of APV ticks at FED
Idea now well thought-outProcedure implemented in basic form using XDAQ
Tested in recent beam/system-tests >1 control ring>1 prototype FED
Standalone operation for procedure envisaged in final system
Local triggerLocal DAQ - FED spy channel/VME
Idea is that this functionality is available during integration/commissioning
[email protected] LECC 2003 CMS Tracker Synchronization
APV ‘tick-marks’
APVs ‘tick’ every 70 clock cyclesstarting at a fixed time after ‘re-synch’ (101) signal received at APV
Tick transmitted over analogue optical link to FEDMeasure arrival time at FED (trigger with APV frame OFF)Knowing analogue optical link lengths (from database)
know time when the ticks left the APVstherefore use ticks for precise probe of timing skew between APVs
‘101’ receivedat APV
tick tick
70 (40MHz) clock cycles 1.75μs
11clock
cycles
time
APV
outp
ut
[email protected] LECC 2003 CMS Tracker Synchronization
TK front-end relative synchronization
At level of 1 control ring/FEDrelative delays due to
position of APV around the control ringanalogue link fibre length
Build up detailed picture of ticks by sweeping front-end TPLL delay at front-end in 1ns steps
Knowing analogue fibre lengths then synchronize APVs using the programmable skew on TPLL
XDAQ implementation for beam and system tests
L. Mirabito, B. Trocmepreviously N. Marinelli
AP
V ti
ck s
igna
ls tr
ansm
itted
to F
ED
Time
‘101’ sent from FEC Different arrival times of ticks at FED- fibre lengths- APV position in control ring
Expand method to cover different control rings in partition by comparing signals on different FEDs
Only ~1 channel/FED needed since inside rings, all APVs already synchronized
Length of TTC cables to FED must also be known!
[email protected] LECC 2003 CMS Tracker Synchronization
TK back-end (FED) synchronization - 1
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Am
plitu
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7550250-25Time (ns)
Can use APV ticks also to set-up delay FPGAs to synchronize FEDsFine skew setting – optimizes analogue signal settling & S/NCoarse skew setting – signals from same APV pipeline locations processed
e.g. pedestal subtraction…..
Do at same time as synchronizing front-end APVs using ticks
(a) APV signals at FEDOptimum sampling point
Front-end FPGAs
Delay FPGAs
[email protected] LECC 2003 CMS Tracker Synchronization
TK back-end (FED) synchronization - 2
e.g. CMS/TOB tests at CERN
J. Valls et al,
this workshop
FED 0
FED 1
FED 2
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Alignment of ticks at FED ensures that APV analogue signals aligned in time for the FED front-end FPGA
[email protected] LECC 2003 CMS Tracker Synchronization
TK relative synchronization summary
DOH
CCU
CCU
CCU
CCUCCU
CCU
CCU
CCU
PLL
APV
FEC
FED
TTCrx
TTCrx
LHCCK
T1,RST,CAL
TTC
AOH
set timing on delay FPGA at FED
Compensate delays at front-end PLLsaround ring
All fibre lengths to FEDs including TTC fibre must be known
Fibre lengths to/from FEC and cables around ring good to know but not critical
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24020016012080400time [nsec]
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[email protected] LECC 2003 CMS Tracker Synchronization
Absolute synchronization of CMS Tracker
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Relative synchronizationto set up the Tracker
Absolute synchronizationto find the particles…
Relative synch aligns APVswith respect to one another
but not to LHC collisionsor rest of CMS
Need to align APV sampling to signal generated in silicon strips by passing particles
Coarse timingadjust latency at APV
Fine timingre-adjust PLLs at front-end
Same procedure as used in beam-tests.
requires:Simple trackingGlobal TRIDAS
Deconvolution
Peak mode
[email protected] LECC 2003 CMS Tracker Synchronization
TK synchronization summary
DOH
CCU
CCU
CCU
CCU
CCU
CCU
CCU
CCU
PLL
APV
FEC
FED
TTCrx
TTCrx
LHCCK
T1,RST,CAL
TTC
AOH
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360
320
280
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200
160
120
Am
plitu
de (A
DC
cou
nts)
7550250-25Time (ns)
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300
200
100
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ADC
Cou
nts
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Question of how to monitor state of synchronization?
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24020016012080400time [nsec]
pre-rad 1 Mrads 4 Mrads 10 Mrads 20 Mrads 20+anneal
[email protected] LECC 2003 CMS Tracker Synchronization
Checking synchronization
TK+ECAL TK+MU
Coarse timing defects easy to see Fine setting problems more difficult
Details of when/how to react to problems to be defined
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ADC C
ounts
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Digital header
Tracker data should be consistent with rest of CMS
FED occupancy should match LHC bunch structure
FED compares 8-bit APV pipeline address in header on every channel with that sent from APVE
[email protected] LECC 2003 CMS Tracker Synchronization
Conclusions
Timing issues in CMS Tracker well understoodconfident of ability to synchronize final components and whole system
Could be ready and debugged in advance of LHC collisions
Relative synchronization procedure based on use of APV tick-markssimple, robust, minimal requirements
Already integral part of start-up procedure for analogue readout systemImplemented in XDAQ, and tested at level of >1 FEDs/FECs
system hardware specs/requirements had synch. procedure in minde.g. Optical link fibre lengthse.g. FED timing skew provision, scope mode and spy channel
Absolute synchronization then done by setting correct latency at APV and adjusting PLL fine delays for maximum S/N
as in beam tests
Can monitor APVs and FEDs for losses of synchronization during running
Next steps: further testing, automation and up-scaling of procedures