LHCb Readout Unit


Block diagram of the RU prototype motherboard (photo)
The LHCb experiment will use S-LINK in the prototype of the Readout Unit. The Readout Units (RU) receive event fragments from several front­end links and assemble them into larger sub­events. Once a subevent is assembled, the RU transfers it to the next stage for further event building. The multiplexing factor in the RU is chosen to match the bandwidths on its inputs with the output bandwidth towards the readout network. 

The RU is connected to a concentrator and the read-out network. The data will be received from this concentrator module which in turn receives its data from four to eight front-end links and sends it out over a single S-LINK. The data rates over those S-LINKs vary between 10 and 60 MByte/sec. The optional S-LINK output connector would allow the RU to be used for Multiplexing only or for diagnostics. The output of the RU will connect to the event builder network. 

Those units are in a low radiation environment (1 to 10 KRad over the lifetime of the experiment). It has to be taken into account that currently no radiation tolerant S-LINK link cards have been designed and that it is the responsibility of LHCb to make sure that such a link will exist in time. 

In the final system 100 Readout Units will be needed, each having between one and four S-LINK inputs.

Photo of the RU prototype (Jan 2000)



2 February 1999 Design started, components for two prototypes will be ordered. Prototype expected to be ready in Summer 1999
6 August 1999 Design review held
1 December 1999 Board received, debugging started
January 2001 Readout Unit II under test
November 2001 The Readout Unit project for FE and DAQ applications has been declared to be the backup solution at the September LHCb TB. The collaboration agreed to freeze the project with a fully operative exerciser system. For the L1 application the RU is still the main solution.



CERN - High Speed Interconnect - S-LINK
Erik van der Bij - 21 November 2001