S-LINK News 2000


VME64x transition module

22 December 2000. With the S2VME64x transition module it is possible to have up to four S-LINK input on the back of an VME64 externsions crate. This passive module routes all S-LINK signals to the 5-row connectors on P2 and P3. This board has been in use by the Liquid Argon detector of ATLAS since September 2000.
A new transition module is being designed that has small S-LINK buffers on board, an Altera that can reformat and regroup the data coming from four S-LINKs before it being sent to the P2 connector. This active transition module is called the TM4plus1 as it has also an ODIN Link Source Card integrated on the board. The TM4plus1, of which prototypes will be available in June 2001, will allow the ATLAS Tilecal detector to use the LArg Read-out Driver.

COMPASS buys 48 ODIN links

21 December 2000. The COMPASS experiment will base their readout on S-LINK. In the year 2000 the experiment had already bought almost 40 FCS-LINK2 links and just before the end of the year 2000, another 48 ODIN type links (thirty 128 MB/s and eighteen 160 MB/s versions) have been ordered. The COMPASS Frontend Readout Driver and Buffer Module (CATCH) that transmits the data is designed by the University of Freiburg, while the Spill Buffer that received the data on a PCI bus is designed by the Technical University of München.

ATLAS ROD data format VHDL code

30 August 2000. Christoph Schwick has made available VHDL hardware design code that can be used by ATLAS ROD designers.
The AtlasRODFormatter is a VHDL-entity that formats data according to the ATLAS ROD - format proposed in "The event format in the ATLAS DAQ/EF prototype-1" (Atlas Daq note 50: ATL-DAQ-98-129). Data is formatted in order to be sent via an S-LINK. He made it available as it can be of use for other developers who have to implement a ROD on their cards.
The AtlasRODFormatter has been developed for the ALTERA FLEX 10K series. It is used in the MIROD which is the Processor interfacing the LVL1 trigger system with LVL2 and the Data Aquisition. The MIROD is part of the MUCTPI (MUon to CTP Interface).

Another Linux driver

14 July 2000. Jan Evert van Grootheest of the company Control Application Engineering (CAE) has written for NIKHEF a fully interrupt driven driver called SLD for the SSPCI interface for generic Linux kernels. It has a zero-copy architecture and does not use the normal read system call to retrieve data. The bigphysarea patch is not required and the driver supports up to four interfaces in one PC. The driver has been released under the GPL. Already since 1997 Linux drivers for S-LINK do exist.

The world's largest CCD camera will be read out with S-LINK

23 June 2000. At the SPIE's "Astronomical Telescopes and Instrumentation 2000" conference the DAQ system of the Megacam astronomical camera has been presented. Megacam is a wide-field imaging camera being designed for the prime focus of the 3.6m Canada-France-Hawaii Telescope, which will start observations in 2001. Each exposure will produce about 770 MB of data; the mosaic will be read out in about 20 seconds which means that Megacam will produce approximately 100 images (science fields and calibration) per night, ie 77 GB of data each night or about 1 TB of data for an average observing run. All imaging data will be send over four S-LINKs.

One can read in the article "The 40 CCDs of the MegaCam wide-field camera: design and first tests of the front-end electronics." of Jean de Kat et al:

Contrary to usual CCD Controllers, no complex boards have been developped to transfer pixel data on optical fibers to the outside. We use the SLink, developped in CERN (European Organisation for Nuclear Research); it is a commercial optical link composed of two CMC cards. The SLink emitter is easy to implement in a custom Controller since it is seen only as a 32bits synchronous Fifo. SLink can transfer continuous data flow at speed of 100MB/s. In MegaCam, it is in fact limited to 80MB/s by SHARC 21060 link ports (note that is no more true with the next SHARC 21160 device).
The SLink receiver is directly PCI compatible, thus can be inserted in many powerful computers. That makes the Controller output 'standard' and not tied to a particular acquisition buffer. A VxWorks software driver has been written for MegaCam. It consists essentially to initialize the SLink and the DMA in the receiver side at each end of packet. The data are transfered in 1074 pixels packets without use of the available control words. The 4 slow rate return lines are not used, since a second link is present for slow control.
The article concludes:
Thanks to high integration, the MegaCam CCD Controller found its place very close to the detectors without any conflict with other parts of the camera (cryogenic pulse tube, filter juke box, shutter, etc...). It will not put much strain on weight, dimension and dissipation budgets too. It will be at the same time the biggest CCD Controller of the world and one of the most simple.
We are glad that the S-LINK has been able to contribute to this simple design.

Want to know how a link design goes?

15 June 2000. Erik Brandin from KTH Stockholm, was one of the three designers of the ODIN S-LINK implementation. He spent nine months at CERN to design and debug the link cards. After that he wrote his Masters Thesis which describes the LHC accelerator, the ATLAS experiment, the place of S-LINK in ATLAS and the design process of the ODIN S-LINK. If you're interested in the details of a link design, his thesis Development of a prototype Read-out link for the ATLAS Experiment (2.4 MB pdf) will give you some insight.

You'll find out that there are many issues in designing a link. Each time you need to use another type of serializer, you would have to redesign major parts, such as error detection, data mapping and especially the reset protocol. Fortunately when you use a ready-made link such as the ODIN, you will not have to worry about those things as all S-LINK cards are compatible; you just can buy the latest link version, which which at least up to 2001 will be the ODIN in either the 128 MB/s or 160 MB/s flavor.
Erik's stay at CERN was funded by TTA Technotransfer AB / NFR.

Looking for Pulsars

9 May 2000. The Osservatorio Astronomico di Bologna in Italy is building a Pulsar observation system. This system will be used at the italian 32 meter dish in Medicina  to observe Pulsar radiosources. Long term timing observations of pulsar give information about the interior structure of neutron stars and is useful in the understanding of the evolution of neutron stars. In timing observations, the radiofrequency signal needs to be sampled in the time and frequency domain, in order to dedisperse and detect the radio pulses.
The system uses S-LINK to read the data that is digitised at a maximum frequency of 100 KHz into a PC with the Linux operating system. 

Atlas TileCal takes testbeam data with commercial ROD and ROB

9 May 2000. The Atlas TileCal detector has taken testbeam data with a system in which the Read-out Driver (ROD) and the Read-out Buffer (ROB) consist all of commercially available equipment. Both the front-end links from the detector to the ROD and the ROD to ROB links are using S-LINK technology. Note that currently used link is not radiation tolerant and that it is up to the people responsible for the TileCal detector to design S-LINK boards that can withstand the high radiation levels that will be around in the LHC environment.

S-LINK Pool for CERN

13 March 2000.  The S-LINK team has set up an ordering service for S-LINK equipment.To reduce delivery times, we also have a small stock of most of the items. This service is available only to users in High-Energy Physics institutes working with CERN. If you need any equipment, you may contact directly Patrick Donnat, Erik van der Bij or Robert McLaren. We prefer you to buy it, in which case we will do the ordering and other handling for you. In case you need the equipment only for a short period of time (less than 3 months), you may rent the equipment. Note that currently the S-LINK Pool is not part of the CERN Electronics Pool.
The list of devices that are in the S-LINK Pool can be consulted online.

Nuclear fusion device uses S-LINK in DAQ system

4 January 2000. On 21 December 1999, the ASDEX upgrade nuclear fusion device started making regular plasma measurements with the new reflectometry system - using an S-Link based data acquisition system.
The purpose of this phase-run-away mirowave reflectometer is to measure the rotation of turbulent structures in the plasma. This is achieved by transmitting a microwave signal towards the plasma in an oblique direction, which is reflected in the plasma and detected with a receiving antenna. The rotation speed can be inferred from the Doppler shift of the received microwave signal. This frequency shift appears as a running phase, hence the name "Phase-run-away" diagnostics.

Short data sheet:

The ASDEX Upgrade tokamak (Axially Symmetric Divertor EXperiment) went into operation at Garching in 1990. This fusion device, Germany's largest at present, is for investigating crucial problems in fusion research under reactor-like conditions. For this purpose essential plasma properties, particularly the plasma density and the wall load, have been adapted to the conditions that will be present in a future fusion reactor.

Old S-LINK News

CERN - High Speed Interconnect - S-LINK
Erik van der Bij - 7 June 2001