Real-time software for the wire per wire X-ray data acquisition system

This paper presents the software developments associated with the design and construction of a fast wire per wire detector system that will be used for high-speed data collection of linear time-resolved X-ray diffraction spectra. As the overall hardware architecture of the system relies on the extensive use of a standard RISC based plug-in module, the code implementation of some critical parts of the software needed careful design to meet the system specifications. The software running on the RISC processor of each acquisition board carries out the high-speed time-resolved histogramming function. This software also deals with the real-time data transfers to the host upon user requests (for display purposes). As time frames can be as short as 5 /spl mu/s, very efficient interrupt handling routines, coded in assembly language, needed to be written to maintain data integrity. We developed a communication protocol to specify the information transfer between the host platform and the acquisition modules. This information is exchanged via an optical link used to connect the remote part of the data acquisition hardware. The software, stored in the crate controller, interprets the host requests and handles the transfer of the resulting low-level instructions to the acquisition boards. It also takes care of the data transfers and the translation into other modules included in the system (e.g. the DAC board used to set the thresholds for the front-end electronics). To allow further upgrades of the acquisition software, a loader module is running on the acquisition boards. Finally, the user software layer, including detector calibration procedures, will be briefly introduced.