An EXELFS multiscalar DMA interface for the IBM PC-AT using programmable gate arrays

An IBM PC-AT interface for data acquisition from diode arrays is described. It was developed for use in an extended energy loss fine structure (EXELFS) spectrometer, where sometimes two diode arrays (containing EXELFS and low-loss spectra) need simultaneous scanning. The system operates as a multiscaler, allowing two processes to be recorded at the same time. The interfaice was designed using a programmable gate array (an 1800 gate-equivalent logic cell array from XILINX) to implement most of the digital circuitry and a 12-bit ADC to sample the analog inputs. A 12-bit DAC was used for analog outputs and for diagnostic testing purposes. The interfaice hardware was given a general design so that it may be used in other e,imilar applications.