Speaker
Description
Summary
TileCal is the hadronic calorimeter of the ATLAS experiments. It consists,
electronically speaking, of 10000 channels to be read each 25 ns. Data
gathered from these channels are digitized and transmitted to the data
acquisition system (DAQ) following the assertions of a three level trigger
system.
The main component of the back-end electronics of the TileCal sub-detector is
the Read-Out Driver (ROD) which is placed between the first and the second
level trigger level. The ROD has to pre-process and gather data coming from
the Front End Boards (FEB) and send these data to the Read-Out Buffers (ROB)
in the second level trigger.
To reduce data loss due to radiation effects, the TileCal collaboration decided to
include data redundancy in the output links of the FrontEnd. This was
accomplished using two optical fibres which transmit the same data. At ROD
system level, data redundancy is used to discard the fibre with errors due to
radiation.
The checking is based on rightness of the Cyclic Redundancy Codes (CRC) of
the data packets on both fibres. This is also necessary as the ROD
motherboard is expecting just one fibre per channel. For this purpose a new
module, called Optical Multiplexer Board (OMB) was conceived. This board would
be able to provide, in case of error in one link, the correct data to the ROD input
by analyzing the Cyclic Redundancy Codes (CRC) of the data packets on both
fibers coming from the FEB.
In the development of the work a new functionality for OMB was proposed.
Because RODs should be tested in production stages and provided that in the
first moments of LHC operation data may not always be available from front-
end, it was suggested to include a “Data Injector Mode” to use the OMB like
data pattern injector for ROD test and verification tasks.
The interest of this project was justified in February 2003, when a preliminary
study appeared. This proposal shown a solution for OMB based on exhaustive
on-line analysis of the data carried by both of the fibbers, using FPGAs for
implementation.
The excellent results of the first OMB 6U prototype are described in this paper
as well as the functional description and technical specifications of the final OMB
9U prototype. In this paper we show the status of this new OMB 9U Prototype.
