Report on the ALICE Detector Data Link: method used, protocol and design status

Paper: 255
Session: B (talk)
Speaker: Rubin, Gyorgy, CERN, Geneva
Keywords: data acquisition systems, FCS

Report on the ALICE Detector Data Link: method used, protocol and design

P.Csato, T.Kiss, Z.Meggyesi, G.Rubin, L.Szendrei, G.Vesztergombi
H-1525 Budapest P.O.Box 49. Hungary

G.Harangozo, I.Novak
Technical University of Budapest
H-1111 Budapest, Muegyetem rkpt. 3. Hungary

H.Beker, W.Carena, R.Divia, M.Macowicz, A.Vascotto, P.Vande Vyvre
CH-1211 Geneva 23. Switzerland

ALICE collaboration


The future LHC experiments are planning to use more than 200.000 links for
the connection of the different layers of the front-end electronics and
the data-acquisition system. In several cases industrial products can be
used, however for some applications special solutions are needed by the

The ALICE DAQ group at CERN and the RMKI (Budapest) are developing a new
link for interfacing the data-acquisition system (DAQ) and the
front-end electronics of the ALICE experiment. This link (called detector
data link or DDL) will provide high-speed transmission of data blocks
(e.g. event data, thresholds, pedestals) in both directions between the
front-end electronics and the read-out receiver cards over a distance of
200 m. The DDL can also be used as a transmission medium for the remote
control of the front-end electronics during the normal operation and for
the remote debugging during the system integration of the ALICE detector.

The ESA PSS-05 software engineering standard has been used for the
development of the DDL. The user requirement document has been prepared.
It specifies the functionalities of the DDL and the interface between the
DDL and the external systems (read-out receiver card, front-end
electronics). The following main technical requirements have been
- bi-directional data transmission with a rate of 100 MByte/s
from the front-end electronics to the read-out receiver card
and a 10 MByte/s rate in the oposite direction;
- detected bit error rate < 10exp-15;
- non detected bit error rate < 1/year;
- mean time to failure > 10 years;
- power consumption of the interface units < 5 W;
- footprint of the interface units < 50 cm2;
- maximum distance between the both ends of the link < 200 m;
- 32 bit data width in both directions;
- built-in self-test mode;
- flow control for data transmission in both directions;

The protocol, the harware and the software model of the interface units
have been defined. A formal method (LOTOS) has been used for the protocol
design and verification.

For the first implementation of the DDL Fibre Channel components and a
subset of the Fibre Channel protocol will be used for the physical layer
of the link.