RISC mezzanines for controlling data acquisition in the NA48 experiment at CERN

A part of the LKr calorimeter data acquisition system of the NA48 experiment (a precision measurements of $\epsilon'/\epsilon$ in CP-violating $K^{0} \to 2\pi$ decays) is described. The experiment runs on the SPS north area in CERN. This paper presents some aspects of controlling the NA48 readout process based on commercial RIO 8260 RISC processors, which were used as a core for maintaining control algorithms. Several RISC processors were equipped with custom-made VME mezzanine boards providing interfacing, pre-processing and data formatting. These mezzanines are the subjects of this paper. They are: RIO-TIC/DAT (a time-stamp distributor and buffered DT-bus interface), FOL-RIO (an optical data formatter and event merger) and "TAXI receiver" (for handling trigger data of the NA48 Level-2 trigger supervisor). Also, the interface between the DT-bus and S- link/PCI is described.