The Napoli group has made the project and the realization of two types of hardware readout controllers: the ROCK,   housed in each level-1 VME crate and the ROCKM (ROCK Manager) housed in each level-2 VME crate.

Data collected by the front-end electronics are read upon a trigger by the ROCK through an auxiliary custom bus (the AUXbus), also designed by the Napoli group.
AUXbus has block transfer capability and can  sustain 50 Mbytes/s.

Data are then bufferized into a decoupling FIFO in the ROCK board which also builds up in hardware a sub-event.

FEE crates form a chain. Through a Chainbus, also designed by the Napoli group, data are sent to a level-2 crate where they are collected by the ROCKM wich organizes chain  sub-events and store them into a decoupling FIFO.

A VME processor (based on ALPHA chip) reads the ROCKM FIFO in block-transfer mode, and send sub-event streams to the farm via FDDI under the control of a Data Flow Controller.

A second level trigger is distributed to the ROCK and the ROCKM and from them receives the busy and halt signals.