hardware implementation of data compression ... - INFN Bologna

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1D compression algorithm and implementations
quisition system, or the SIU can leave the bidirectional buses control to
CARLOS for an other data event to be sent. So far, CARLOS begins
waiting 16 foclk periods: if nothing happens, CARLOS is able to begin
sending data again without the need to receive some other commands
from the SIU; if the SIU takes back the possession of the bidirectional
buses, CARLOS closes the link towards the SIU and keeps waiting for
an other RDYRX command raised from the SIU itself.
The feesiu block implements this communication protocol with the SIU
using a simple state-machine: for example state 0 is the state in which
CARLOS is waiting for a command of initialization from the SIU, state
1 is the state in which CARLOS sends data from the SIU, state 2 in
which CARLOS sends the front end status word to the SIU, state 3
in which CARLOS waits 16 foclk periods waiting for some action from
the SIU to happen.
An important feature of CARLOS realized in the feesiu blockisthe
following one: CARLOS cannot accept a new event before the previous
one has been completely sent in output, otherwise we run into the
risk of mixing data belonging to different events. The only way CAR-
LOS has to implement back-pressure on the AMBRA chips is using the
wait-request signals. So far the wait-request signal has to avoid that
CARLOS fetches new input data values while emptying the FIFOs.
For this reason a new signal, dont-send-data, has been introduced for
every macro-channel which turns to 1 when the end-trace is activated
and turns back to 0 when all the FIFOs are completely empty. So
the wait-request of every macro-channel is obtained by putting in OR
the full and dont-send-data signals. The feesiu acknowledges that all
the FIFOs have been emptied using the empty signal of every FIFO
block. When all the 8 signals turn to 1 the feesiu block raises the allfifos-empty
signal which stands at logical level 1 for at least two clock
periods in order to be sensed by the foclk clock. The all-fifos-empty signal
is also used to trigger the event-counter block: in fact the number
of total events is exactly the same as the total number of occurrences
of the all-fifos-empty signal. An other signal, end-trace-global is set to