36
2 Front-End Electronics
buffer implemented in the SAMPA was kept to avoid the additional risk and work of
reducing the memory size.
2.4.3.3 Bandwidth MCH
The MCH is targeting an interaction rate of 100 kHz with 9% channel occupancy.
3
With a pulse shaping time of 300 ns, the average number of samples above the zero
suppression threshold is 10 when the sampling frequency is 10 MHz. The bandwidth
available per front-end card is 80 Mb/s, which is shared between the two chips and
gives 40 Mb/s per chip.
As described earlier in Sect. 2.4.3, the SAMPA data transmission operates on a
packet basis where a packet contains a header of 50 bits and a payload of compressed
sample data. The amount of time-bins per packet is programmable up to 1023 bins.
If no data is above the zero suppression threshold for the full duration of a packet, the
chip would normally send only the header with an empty payload, but it is possible
to set the chip to suppress these packets to save bandwidth.
The data rate for each of the possible operations modes of the MCH can be
calculated directly, if we assume that there is no noise that creates false clusters.
BW trigger wo/empt y = H b · f i · N ch · P occ +
D b · f i · N ch · P occ
(2.3)
BW trigger w/empt y = H b · f i · N ch +
D b · f i · N ch · P occ
(2.4)
BW cont wo/empt y = H b · f pkt · N ch · (1 − (1 − P occ )
f i
f pkt ) +
D b · f i · N ch · P occ
(2.5)
BW cont w/empt y = H b · f pkt · N ch +
D b · f i · N ch · P occ
(2.6)
Where BW trigger wo/empt y in (2.3) is the bandwidth needed for triggered mode with
suppression of empty packets, BW trigger w/empt y in (2.4) is the bandwidth needed
for triggered mode without suppression of empty packets, BW cont wo/empt y in (2.5)
is the bandwidth needed for continuous mode with suppression of empty packets,
BW cont w/empt y in (2.6) is the bandwidth needed for continuous mode without suppression of empty packets. BW x is given in bps. H b is the 50 bits of the header, f i
is the interaction rate, f s is the sampling rate, f pkt is the packet rate which is the
sample rate divided by the programmed length of a time window, N ch is the number
3 Channel occupancy is the fraction of channels that register a hit per interaction.
2 Front-End Electronics
buffer implemented in the SAMPA was kept to avoid the additional risk and work of
reducing the memory size.
2.4.3.3 Bandwidth MCH
The MCH is targeting an interaction rate of 100 kHz with 9% channel occupancy.
3
With a pulse shaping time of 300 ns, the average number of samples above the zero
suppression threshold is 10 when the sampling frequency is 10 MHz. The bandwidth
available per front-end card is 80 Mb/s, which is shared between the two chips and
gives 40 Mb/s per chip.
As described earlier in Sect. 2.4.3, the SAMPA data transmission operates on a
packet basis where a packet contains a header of 50 bits and a payload of compressed
sample data. The amount of time-bins per packet is programmable up to 1023 bins.
If no data is above the zero suppression threshold for the full duration of a packet, the
chip would normally send only the header with an empty payload, but it is possible
to set the chip to suppress these packets to save bandwidth.
The data rate for each of the possible operations modes of the MCH can be
calculated directly, if we assume that there is no noise that creates false clusters.
BW trigger wo/empt y = H b · f i · N ch · P occ +
D b · f i · N ch · P occ
(2.3)
BW trigger w/empt y = H b · f i · N ch +
D b · f i · N ch · P occ
(2.4)
BW cont wo/empt y = H b · f pkt · N ch · (1 − (1 − P occ )
f i
f pkt ) +
D b · f i · N ch · P occ
(2.5)
BW cont w/empt y = H b · f pkt · N ch +
D b · f i · N ch · P occ
(2.6)
Where BW trigger wo/empt y in (2.3) is the bandwidth needed for triggered mode with
suppression of empty packets, BW trigger w/empt y in (2.4) is the bandwidth needed
for triggered mode without suppression of empty packets, BW cont wo/empt y in (2.5)
is the bandwidth needed for continuous mode with suppression of empty packets,
BW cont w/empt y in (2.6) is the bandwidth needed for continuous mode without suppression of empty packets. BW x is given in bps. H b is the 50 bits of the header, f i
is the interaction rate, f s is the sampling rate, f pkt is the packet rate which is the
sample rate divided by the programmed length of a time window, N ch is the number
3 Channel occupancy is the fraction of channels that register a hit per interaction.