Speaker
Description
The LHC-synchronous part of the Phase-2 CMS DAQ and timing systems
will be built around two custom ATCA boards, interfacing the
subdetector back-ends to the central trigger-DAQ systems. The DAQ and
Timing Hub provides a 10 Gb/s connection to the central timing system,
and up to 400 Gb/s of DAQ bandwidth. This board can be combined with
one/multiple DAQ800 boards to increase the data bandwidth.
With the prototyping phase completed, we now present our first
experience with partial- and full-chain systems, demonstrating the
core of the Phase-2 CMS DAQ, timing, and trigger control systems.
Summary (500 words)
The LHC-synchronous part of the Phase-2 CMS DAQ and timing systems
will be built around a pair of custom ATCA boards, interfacing the
subdetector back-end electronics to the central trigger-DAQ
systems. The DAQ and Timing Hub (DTH400) forms the main back-end
interface, and one DTH400 will be located in each of the ATCA crates
housing the back-end electronics. The DTH400 provides a 10 Gb/s
bidirectional connection to the central timing and trigger control
system, and up to 400 Gb/s physics data bandwidth to the central DAQ
system. Physics data are aggregated from up to 24 custom-protocol
back-end links, and output on up to four 100 GbE standard Ethernet
ports. For subsystems requiring more throughput, the DTH400 can be
combined with one or multiple DAQ800 boards. Each DAQ800 board
provides twice the DAQ bandwidth of the DTH400, on twice the input and
output link count. The DAQ800 only implements the data aggregation
functionality and receives its timing and trigger information from the
DTH400 in the back-end crate.
During the prototyping process, the recent increases in component lead
times and obsolescence hampered the convergence of the final
design. For example: the on-board controller used for the DTH400 and
DAQ800 boards, which, for reasons of space and functional
factorisation, is placed on a Rear Transition Module (RTM), had to be
changed due to lack of availability. This required a redesign of the
RTM and the corresponding boot and configuration firmware and
software. At the same time, this did demonstrate the flexibility of
the RTM-based design.
The limited amount of prototype boards available so far necessitated a
piece-wise development approach, where small parts of the overall
system were implemented and tested one at a time, repurposing the
boards for different tasks in each and every step. Now, with more
boards becoming available, several larger-scale systems are being
assembled.
These systems can be grouped along two scaling axes': the timing
system scaleshorizontally' to the synchronisation of multiple
crates, with a configurable switch grouping crates into independent
runs, whereas the DAQ system scales `vertically' along the data
aggregation and event reconstruction/selection path. The possibility
to operate multiple crates in-sync also opens up the path towards
integration of the Level-1 trigger system in its final architecture,
spanning several crates housing multiple board types, interconnected
with optical links of different lengths and latencies.
This paper focuses on our first experience with these demonstrator
systems, showcasing the core of the Phase-2 CMS DAQ, timing, and
trigger control systems. For context, it summarises how the
prototyping of individual functionalities was led to converge for this
system-level integration and development.
