Data Routing Module
The DRM performs a number of important tasks:
- It receives trigger requests from the TIC and makes them available to the PMBs in the crate.
- After trigger reception, it decides when to start a readout procedure.
- During readout operations, it arbitrates the bus.
- It collects read out data on a FIFO and dispatches them to the ROC, which formats and sends them to the NA48 Data Merger via the VFIFO.
All these operation have to be executed concurrently. The DRM uses a custom readout protocol. Data transmission speed on the VME bus is about 60 MBytes/s without using block transfer, which is not possible when performing zero suppression. All the readout operations can be performed in a slower way by means of the SBC, if the DRM allows it to master the VME crate. This is extremely useful during DAQ channels test procedures.