K. Gill CERN EP/CME B. Trocme, L. Mirabito Institut de ...musico/TotemDoc/B3.3-Gill-Tracker_synch_LEB_03.pdfInstitut de Physique Nucleaire de Lyon. [email protected] LECC 2003 CMS

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


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


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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��

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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


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


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


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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pre-rad 1 Mrads 4 Mrads 10 Mrads 20 Mrads 20+anneal

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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


Timing issues: back-end (FEDs)

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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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DC

cou

nts)

7550250-25Time (ns)

Optimum sampling point


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


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


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


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!


TK back-end (FED) synchronization - 1

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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


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


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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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


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

240

200

160

120

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plitu

de (A

DC

cou

nts)

7550250-25Time (ns)

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300

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Cou

nts

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Question of how to monitor state of synchronization?

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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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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


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

Documents

K. Gill CERN EP/CME B. Trocme, L. Mirabito Institut de ...musico/TotemDoc/B3.3-Gill-Tracker_synch_LEB_03.pdfInstitut de Physique Nucleaire de Lyon. [email protected] LECC 2003 CMS