The read-out driver for the ATLAS MDT muon precision chambers

The 1172 Monitored Drift Tube (MDT) precision chambers of the muon spectrometer of the ATLAS experiment at the LHC will be read out by 204 MDT Read-Out Drivers (MRODs). The MRODs receive event data via 1136 optical links (up to 6 per MROD), build event fragments at a maximum rate of 100 kHz, output these to the ATLAS data-acquisition system and take care of monitoring and error checking, handling and flagging. The evolution of the design of the MROD (a 9U VME64 module in which this functionality is implemented using FPGAs and ADSP-21160 Digital Signal Processors programmed in C++) is reviewed and critical issues are discussed.