Back-end and interface implementation of the STS-XYTER2 prototype ASIC for the CBM experiment

Abstract

Each front-end readout ASIC for the High-Energy Physics experiments requires robust and effective hit data streaming and control mechanism. A new STS-XYTER2 full-size prototype chip for the Silicon Tracking System and Muon Chamber detectors in the Compressed Baryonic Matter experiment at Facility for Antiproton and Ion Research (FAIR, Germany) is a 128-channel time and amplitude measuring solution for silicon microstrip and gas detectors. It operates at 250 kHit/s/channel hit rate, each hit producing 27 bits of information (5-bit amplitude, 14-bit timestamp, position and diagnostics data). The chip back-end implements fast front-end channel read-out, timestamp-wise hit sorting, and data streaming via a scalable interface implementing the dedicated protocol (STS-HCTSP) for chip control and hit transfer with data bandwidth from 9.7 MHit/s up to 47 MHit/s. It also includes multiple options for link diagnostics, failure detection, and throttling features. The back-end is designed to operate with the data acquisition architecture based on the CERN GBTx transceivers. This paper presents the details of the back-end and interface design and its implementation in the UMC 180 nm CMOS process.

SMX and front-end board tester for CBM readout chain

“…Testing all produced ASICs, assembled FEBs, and full modules is the essential quality verification step in the production process [8,9]. The SMX contains complex analog [10] and digital [11] functionality controlled via a rich set of registers accessible with a dedicated Hit Control Transfer Synchronous Protocol (HCTSP) [12]. The same protocol is also used to send the received hit data to the data acquisition system.…”

Throttling Studies for the CBM Self-triggered Readout

“…The ASIC counts the number of channels with almost-full FIFOs. The channel threshold triggering an alert is programmable [4]. If exceeded, the ASIC reports an almost full condition to the CRI by sending an alert frame.…”

“…In the data flow model shown in figure 2, the maximum number of 5 readout elinks/ASIC are active [4], resulting in 50 MHits/ASIC/s as bandwidth limit. The corresponding drain time of the…”

The powering concept of the Silicon Tracking System for CBM@FAIR

“…2). Silicon strip detector signals are read out via micro-cables by corresponding readout SMX ASICs (STS-MUCH-xyter [1] [2] [3]) located on Front End Boards (FEBs).…”