Speaker
Description
Summary
- INTRODUCTION
The Optical Multiplexer Board (OMB), also known as PreROD,
will be the module which
will decide which of the two optical fibers coming from the
Front-End (FE)
electronics of the TileCal detector carry error-free data. This
is necessary
because
radiation inside the detector can produce malfuntioning of
the digital circuits of
the FE. To solve this problem two optical fibers come out
from the FE carrying the
same data. Should radiation produce any error, the OMB will
detect it by checking
the CRC codes for the data packect and select the error-free
fiber.
A first prototype of this OMB is already functioning and used
for ROD commisioning
tasks. This prototype only includes two input channels (4
input fibers) and two
output channels (2 fibers) and is implements in a VME 6U
board. A brief description
of this board is presented in the next section.
- OMB 6U prototype
The basic building blocks of the 6U prototype are:
- the VME slave controller
it operates the whole board, keeping records on
the number of errors
detected in each channel, and sets its working mode which
can be normal or
injection. This second mode allows the OMB to inject data
blocks either
automatically or previously loaded from VME.
- the CRC and link controller
it holds two input and one output high-speed link
controller and the CRC
algorithm calculation and checking logic. It's connected to
the VME controller for
control and debug operations.
The prototype has two CRC and link controller blocks, one
per input channel, and
one
VME slave controller.
One of the most interesting functionality of the board,
provided the TileCal
detector is not yet built, is the injection mode. With this
mode it has been
possible to carry out ROD commissioning tasks at Valencia
thanks to the possibility
of injecting known data blocks and the selection of trigger
inputs, either
internally generated or input from NIM logic.
- OMB 9U description and current work
The good results achieved from the 6U experience are being
now used to define the
final OMB prototype. This prototype is conceived in a 1 to 1
ratio with respect to
RODs. This is to say that each final prototype will have 8
input channels (16
fibers) and 8 output channels (8 fibers). Due to this
modification a 9U format has
been chosen for this new implementation.
With respect to functionality there are some minor
modifications among of which,
the
inclusion of the TTC receiver chip is the main one. This would
lead to the
possibility of having trigger directly from the TTC system,
something which is not
possible now.
Electrically speaking the new board poses some problems
related to signal integrity
and component placement issues. The use of a single JTAG
chain for the programming
of all the FPGA chips in the board and the bus connecting
the VME controller and
the
CRC controllers are the main issues. Simulation of this
connections as well as
firmware modification in the FPGA used are part of the work
currently going on and
that will be included in the presentation.
