In GPI-300 the digital electronics unit for the control and data acquisition was developed on the basis of the digital signal processor (DSP) ADSP-2181. It consists of control logic, RAM and SRAM, ADCs and DACs of a high word length (up to 20 bits), high-voltage amplifiers (HVA ±150V) and generators (see the diagram below). The software allows to carry out structural and spectral measurements of any degree of complexity. Flexible architecture of the unit and software can be adjusted easily for various types of scanners.

The control system consists of:

The digital electronics unit;

Low-noise I-V converter in UHV design mounted directly on the scanner;

Preamplifier and filters connected to electrical feed-throughs of the vacuum module;

Host computer;

Two levels of the software (the low one - the program loaded in DSP and the top one - the program, running on the host-computer). The software performs various types of scanning: a mode of a constant tunnel current, a mode of constant height, a mode of work-function mapping, a special mode of measurement and elimination of both drift and slope distortions of an image (and for initial piezo-ceramics calibration as well) [V.Yu. Yurov, A.N.Klimov, Rev. Sci. Instrum.65 (1994) 1551]. Besides there is a mode of V-I or Z-I spectroscopy in any point of the image and lithography mode as well.