Enrico Fois - LHCb Muon ECS Meeting - Roma 06-04-2006 1 Synchronization and alignment requirements

Enrico Fois - LHCb Muon ECS Meeting - Roma 06-04-2006

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Synchronization and alignment requirements


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Synchro Problem

Signals generated by the same BX interaction and coming from

different Physical Channels have different delays

To reach the maximum efficiency of the muon detector we must:• Measure time arrival of signals with a precision of 1-2 ns • Have the possibility to delay signals with the same accuracy (Fine time)• Synchronize signals with the same BX Id (Coarse time)

We can perform this tasks with DIALOG, SYNC and TTCrx devices


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Synchro ToolsSYNC chip can:• histogram incoming signals with a precision of ~ 1,56 ns (16 bins in

the 25 ns window)• delay signals of an integer number of BX ID, up to 10 clock cycles

TTCrx chip can delay signals of an integer number of BX ID, up to 15 clock cycles

DIALOG chip can delay signals at steps of 1.67 ns up to 50 ns


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Synchro toolsThe control of these devices is done by ECS via CANbus protocol

Synchronization procedure must get access to DIALOG and SYNC by the ECS infrastructure (CANbus protocol – PVSS software)

CANbus is managed by the ELMB board (one for each ODE, four for each SB)


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Synchro in practice

Muon system is composed of about 120000 physical channels

For each of these the fine time histogram is required to align the signal distribution at the centre of the reference clock period (Fine time)

It translates into two main actions:

put SYNC chips in FT histogram mode, wait for acquiring sufficient statistics and then download histo data to analize

assign the appropriate delay to signals writing DIALOG delay registers


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Synchro in practice

We will shift the signal distribution as follow:

BX n

TIME DISTRIBUTION

BX n

TIME DISTRIBUTION


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Synchro in practice

Next step take is to set the correct BX tagging (Coarse time)

It translates into two main actions:

put SYNC chips in BX histogram mode, wait for acquiring sufficient statistics and then download histo data to analize

assign the appropriate delay to signals writing SYNC delay registers


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Synchro in practice

We will shift the BX tagging ID as follow:

Coarse time procedure takes into account the LHCb bunch orbit

BX n (wrong)

TIME DISTRIBUTION

BX n–3 (right)

TIME DISTRIBUTION


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Time problems

BUT…

This procedure would take a huge amount of time (too much!!!)

The idea is to consider the same delay for close channels

and to parallelize the procedure where possible (different I2C chains)


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Synchro procedureSynchronization procedure for Fine time is sketched in the flow chart below:


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Synchro procedureSynchronization procedure for Coarse time is sketched in the flow chart below:


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Time evaluation

Here a time evaluation to synchronize all the muon system

Thanks to Caterina Deplano


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Syncro & ECS

All the registers involved in the synchronization tasks are only accessiblevia ECS (CANbus – I2C)

These procedures will be developed inside the ECS - PVSS environment

Crucial requirement is to have implemented all the CANbus features for SB and ODE (inside the PVSS framework…)


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DIALOG & SYNC reg queries

The synchronization procedure have to get access to DIALOG chip only to write delays

The main question is: how much the distributions will move in time?

(to be investigated…)

SYNC access will be more frequent to monitor FT distributions

We suppose Coarse time delays will not change in time


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Histo download timeA single histogram download from SYNC to PVSS takes about 350 ms… (I2C clock?...Is it a negligible detail?)

…up to 24 SYNC per ODE less than 9 seconds!

Can we parallelize downloads?

Data transfer from SYNCs to ODE ELMB is implemented via SDO, thus the client have to wait server response…

parallelization is possible for each single CAN branch but not for nodes

Question: how many nodes for each branch???

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Enrico Fois - LHCb Muon ECS Meeting - Roma 06-04-2006 1 Synchronization and alignment requirements