Speaker
Description
Summary
The GPL board is an optical pattern generator used for the external test bench of
the Level0 Decision Unit. Its design is based on three FPGAs in BGA package which
can send 24*16 bits @ 80 MHz via 24 optical fiber link running at 1.6 Gb/s.
One FPGA is used for the control of the board and two processing FPGAs are used to
control the optical channel. Each processing FPGA controls twelve deserializers
which send the data to an optical transceiver. For stand alone test purpose, an
additional single optical channel transceiver is implemented. The GPL board is
synchronized by the Timing and Trigger Control which delivers, through the TTC
mezzanine and the QPLL, the clock reference with low jitter required by the
deserializers. A 32 bit LVDS input is implemented in order to receive the Readout
Supervisor word from the L0DU. The acquired data is saved and compared to the
expected results to elaborate the diagnostic of test. The GPL board allows to
emulate the full L0DU environment at laboratory and will be the same rack of the
L0DU for the commissioning test.
Two tests mode are foreseen. The first one consists in sending a 16 bits counter one
every optical fiber link in order to qualify the bit error rate of each optical
fiber link. The second test, the content of FPGA's internal memory or external
memory is sent to the L0DU to check the behaviour of the L0DU. This mode allows
testing the L0DU algorithms with realistic data generated from a sample of simulated
physics events, and check the behaviour of the L0DU when erroneous data or optical
transfer errors are introduced in the data flow.
To control the board, two interfaces are provided. The first one is an USB interface
based on a commercial device, which allows to connect the board directly to a PC to
configure the board. The second one is done through the L0DU and the CC-PC of the
TELL1 board. In this configuration, the GPL board is seen as a part of the L0DU and
can be controlled and configured by the Experimental Control System (ECS).
The same software interface is used to configure both boards. It allows to easily
set up the internal register and the pattern RAM with graphical panels and to
analyse the test results. The L0DU environment in the LHCb experiment could be
emulated by the GPL board which is a 16 layer custom board.
It is the central part of the external test bench of the L0DU. It allows to qualify
the bit error rate of each optical fiber link on the receiver side and to emulate
the L0DU input informations which are sent by the L0 sub-triggers.
