We are planning to launch a micro satellite, Kanazawa-SAT3 , at the end of FY2018 to localize X-ray transients associated with gravitational wave sources. Now we are testing a prototype model of wide-field Xray imaging detector named T-LEX (Transient Localization EXperiment). T-LEX is an orthogonally distributed two sets of 1-dimensional silicon strip detectors with coded aperture masks, and covers more than 1 steradian field of view in the energy range of 1 – 20 keV. Each dimension has 512 readout electrodes (totally 1,024 channels), and they are read out with application specific integrated circuits (ASICs) controlled by two onboard FPGAs. Moreover, each FPGA calculates the cross correlation between the X-ray intensity and mask patterns every 64 msec, makes a histogram of lightcurves and energy spectra, and also plays a role of telemetry/command interface to mission CPU. In this paper, we report an overview of digital electronics system. Especially, we focus on the high-speed imaging processor on FPGA and demonstrate its performance as an X-ray imaging system.